Events

We live in an epoch of exoplanet discovery. Within the next decade the discovery of rocky planets orbiting other stars will be commonplace. However, in order to fully understand these exoplanetary systems and their potential to host life, we have to consider the planetary system as a whole. Information from host-star compositions, system architectures and white dwarfs that have accreted planetary material add to our intuition. I will discuss how we can start to think about whether exoplanetary systems have the right material available and the right physical conditions for the origin of life. Our exploration of planetary systems beyond the Solar System goes hand in hand with the journey of discovery of how life on Earth came to be.

Contrary to many stereotypes about massive galaxies, the observed systems are diverse in their star formation rates, kinematic properties, and morphologies. Studying how they evolve into and express such diverse characteristics is an important piece of the galaxy formation puzzle. Here, we focus on a subset of massive galaxies, the brightest group galaxies (BGGs). We use a high-resolution cosmological suite of simulations based on the Romulus galaxy formation model, and compare simulated central galaxies in group-scale halos at 𝑧 = 0 to their observed counterparts. Since most galaxy formation models are calibrated using measures that are strongly influenced by the properties and evolution of “normal” Milky-Way like galaxies, this exercise is also an opportunity to test the limits of these models. The comparison encompasses the stellar mass-halo mass relation, various kinematic properties and scaling relations, morphologies, and the star formation rates. We find Romulus BGGs that are early-type S0 and elliptical galaxies as well as late-type disk galaxies; we find BGGs that are fast-rotators as well as slow-rotators; and we observe BGGs transforming from late-type to early-type following strong dynamical interactions with satellites. In short, we find that Romulus reproduces the full spectrum of diversity in the properties of the BGGs very well. Additionally, due to its superb mass and spatial resolution, Romulus also offers a unique window onto the joint evolution of the BGGs and the surrounding intragroup medium. With respect to the latter, we are able to observe the emergence of multiphase structure - in the form of cold clouds - in the intragroup medium. Groups also experience repeated AGN feedback episodes that drive large-scale collimated outflows into the IGrM. While the present resolution does not allow direct exploration of the coupling between the clouds and the AGN jets, we argue that the clouds will cause the SMBHs (and hence, the jets) to change direction every so often. Returning back to the BGGs, we find that early type galaxies can rejuvenate by growing disks, in agreement with recent observations. However, we also note a tendency towards lower than the observed fraction of quenched BGGs, with increasing halo mass. The problem appears to be due to decreasing effectiveness of AGN feedback with increasing halo mass. Examining some of the other galaxy formation models, we find that they too run into trouble on the same scale — but in an opposite sense. I will conclude by discussing what we are to make of this and what the path forward looks like.

In minor galaxy cluster mergers, several interesting gas dynamics phenomena take place. These include the formation of a bow shock by the supersonically infalling smaller merger partner, an enhanced stagnation point pressure just upstream of the infalling subcluster, gas stripping of the smaller partner, and gas sloshing of the larger host cluster. Theoretical and numerical work has advanced our understanding of these processes and their associated observable signatures. These effects, or similar ones, are also known in Earth-bound gas flows, and simple analytical estimates have been used to derive properties such as merger ages and infall speeds from observations. However, the applied methods often rely on at least quasi-steady gas flow conditions, which can’t be assumed in cluster mergers due to density gradients in the ICM and non-constant merger velocities. I report on two lines of our research: We investigate to what extent the non-steady state nature of gas flows in mergers biases measurements of merger velocities, and we present an analytical toy model for cluster sloshing.

Astronomy studies the history of the universe while archaeology studies the history of the human past. The talk will explore the benefits of interdisciplinary research from fundamental science (e.g. Astrophysics) to applied science and Engineering and how applications to cultural heritage materials can inspire the development of instruments that are useful for industrial monitoring. Inspired by ideas from Astronomy, various remote sensing and interferometric imaging techniques have been developed for cultural heritage material analysis to study history and help art conservation. As the volume of data collected is becoming too large to manage using traditional image analysis methods, machine learning methods are developed to analyse data from automated high resolution large scale surveys of wall paintings such as those in cave temples along the Silk Road. This talk will discuss some of the unexpected contribution of astronomy to the field of heritage science including conservation science and archaeological science.

Merging compact objects in which at least one component is a neutron star can produce several observable phenomena: namely loud gravitational wave chirp signals, radioactively powered kilonovae, and in at least some cases, relativistic jets creating bright flashes of gamma rays. These events have important implications for the heavy element nucleosynthesis budget of the universe, our understanding of jet acceleration, precision cosmology and tests of fundamental physics ranging from the neutron star equation of state to tests of Lorentz invariance. I will review the status of this young field, highlighting some recent surprises, and consider prospects for the coming years.

How galaxies stop forming new stars (quenching) is one of the major open problems in astrophysics. Large spectroscopy survey at z~0-1 have enabled tremendous progress in this field, highlighting the role of AGN in queching massive galaxies. But the advent of JWST is providing new and stringent constraints on the physical processes responsible for quenching, challenging our picture of galaxy formation and quenching. I will start by presenting new results from JWST NIRSpec integral-field spectroscopy of massive, post-starburst galaxies at z~3-5, revealing stellar rotation, a gas-rich CGM, and ongoing AGN feedback. I will then move to lower-mass systems at higher redshifts (possible progenitors) showing evidence of ongoing AGN feedback. I will then discuss internal feedback mechanisms and the open questions about the transition between stochastic star-formation histories and long-term quenching.

Galaxy clusters are among the most special lines-of-sights in Astronomy. In clusters, galaxy evolution is subverted by a fine-grained plethora of physical processes, yet to be fully unraveled. In clusters, gravity shows its wide reach, ranging from its strongest to its most tenuous regime. We are at the beginning of a transformative era for galaxy cluster science thanks to new large-scale multi-wavelength observational campaigns. Conditions are unique to progress the scope of current theories and models describing galaxy and structures evolution by defining new ambitious empirical tests. For instance, numerical simulations offer the ideal test-bench to identify which density regime in the cosmic web yields the strongest imprint on galaxy evolution. In this talk, I will review some recent results on galaxy clusters I've been involved with, and will present how here in Nottingham we are planning to track the evolution of simulated large-scales structures, in particular cosmic filaments, across redshift.

Active galaxies (AGN) are powered by the accretion of matter onto a supermassive black hole (SMBH), which provides an important channel for BH growth and evolution. Key to understanding this accretion process are detailed measurements of BH mass and spin, as well as the mechanisms driving feedback of material into the galaxy through outflows and jets. To make these measurements, we need to resolve the unresolvable inner regions of accreting black holes. This accretion process is observed to vary on all timescales and in all wavebands, with the fastest variations observed in the X-ray band. One of the most exciting results in AGN studies is the recent discovery of reverberation delays in the X-ray light curves. These short (~100 second) time delays allow us to probe the geometry of the X-ray emission region immediately outside the event horizon. In this talk I will discuss the current and future state of X-ray reverberation mapping across the black hole mass range. I will present an extensive X-ray variability analysis from a 2 mega-second XMM-Newton observation of a highly-variable Seyfert 1 galaxy. Modelling of the coronal and reverberation delays using GR ray-tracing models has revealed the most detailed picture to date of the inner X-ray emitting regions of AGN and provides an independent estimate on black hole mass and spin. I will finish by discussing the recent use of machine learning methods to understand this problem.

Galaxies do not grow in isolation, but within a cosmic web of intergalactic gas. The evolution of the galaxies and this intergalactic medium are closely connected. As the first galaxies formed, their light heated the gas surrounding them in a process known as reionization. Measuring the progress of reionization can give us an indirect view of how and when the first galaxies formed, complementary to direct observations of these galaxies with telescopes like JWST. In this talk, I will discuss how we can constrain the timing of reionization with different observational probes, such as absorption in the spectra of distant galaxies and quasars. I will present my work interpreting these observations with large cosmological simulations of the intergalactic medium. I will discuss what is known about the history of reionization, and what questions are still to be answered.

The low-surface-brightness (LSB) universe in the near-IR range remains largely unexplored due to atmospheric brightness limitations in ground-based observations. However, the near-IR holds immense potential for understanding the properties of stellar populations in the outer regions of galaxies, primarily composed of older stars. To bridge this research gap and preserve LSB structures, we have developed a novel and reproducible reduction pipeline for VIRCAM on ESO's VISTA telescope. Our pipeline encompasses an automated process, from data retrieval from ESO's archive to the final co-adding and catalogue production, ensuring high speed and optimised disk space requirements. Leveraging advanced techniques from the powerful GNU Astronomy Utilities (Gnuastro) programmes, we effectively mitigate large flat patterns and large-scale instrument signatures in the intricate structures of VIRCAM detectors. Our primary focus lies in the Ks-band data analysis within the Euclid Deep Field South region (EDFS), although our pipeline is applicable to other VISTA/VIRCAM fields. Exploiting the synergies between VISTA data and complementary observations from Spitzer, Euclid, LSST, WFIRST, JWST, and ALMA in this region holds the promise of captivating discoveries.

The big evolutionary change in the life of a galaxy is its transition from a star-forming to a passive galaxy. In this talk, I will discuss three possible physical mechanisms which can induce this transition, each acting on a different regime of galaxy mass and large scale environment, but all of which are fundamentally related to the available gas content. I will discuss how satellite galaxies lose gas as they slam into the hot medium characterising massive halos, how massive galaxies are limited by their ability to accrete gas from the large scale environment and how intermediate mass galaxies fail to contain their gas after internal explosions.

The upper atmosphere is a tenuous region that defines the planetary boundary to space. Here, spectacular displays of auroral emissions reveal that energy is exchanged from the surrounding space environment and the underlying planetary atmosphere. At Earth, the global temperature of this region is well explained by the energy injected by solar EUV flux. However, the upper atmospheres of the giant planets are much hotter than the solar input alone can produce, a long-standing question dubbed the 'giant planet energy crisis' - where is this additional energy coming from? By observing emissions from the molecular ion H3+, a dominant component of the charted particle ionosphere, we can remotely determine the physical properties of the upper atmosphere. Here, I review our current understanding of this region, how it interacts with both the magnetic field, and the atmosphere below. The latest, greatest set of observations of Jupiter, Uranus, and Neptune, representing gas and ice giants respectively, were recently acquired by the James Webb Space Telescope. These (truly amazing) data-sets provide a completely new view of these planets. Could they provide the key to solving the giant planet energy crisis?

The big evolutionary change in the life of a galaxy is its transition from a star-forming to a passive galaxy. In this talk, I will discuss three possible physical mechanisms which can induce this transition, each acting on a different regime of galaxy mass and large scale environment, but all of which are fundamentally related to the available gas content. I will discuss how satellite galaxies lose gas as they slam into the hot medium characterising massive halos, how massive galaxies are limited by their ability to accrete gas from the large scale environment and how intermediate mass galaxies fail to contain their gas after internal explosions.

Radio-loud Active Galactic Nuclei (AGN) host galaxies are known to produce jets sufficiently powerful to disrupt and even expel gas from their host galaxies. With optical integral field unit (IFU) MUSE observations, we observe rest-UV line emission from gas which is chemically enriched through previous star-forming epochs and also photoionised by the AGN. In cases where the jet axes are aligned with the extended ionised gas morphologies, we find a clear feedback association between the high energy output of the jets and the ionised gas. Additional evidence for such AGN feedback is seen in the very complex Ly-alpha halo morphologies prevalent around radio galaxies at redshifts z=2 to z=5. With ALMA, we trace the cold gas component of the interstellar medium (ISM) in the radio galaxies via neutral carbon emission. These [CI](1-0) line detections trace faint cold gas in emission from which we infer cold molecular gas fractions of <20%. Based on our results, we conclude that gas depletion through star formation and molecular gas outflows driven by the jets may have led to a diminished gas supply in the ISM of our observed radio galaxies. Overall, our MUSE and ALMA studies add significantly to the body of work in galaxy studies that illustrate the impact of AGN-driven jets on star formation. In the second part of the talk, I will discuss recent results based on MeerKAT & uGMRT (superMIGHTEE) observations which highlight the usefulness of deep radio continuum surveys in studying the physical processes underlying radio emission within star-forming galaxies and radio AGN up to z=5.

Disc galaxies are complicated beasts. Acted upon by both internal and external evolutionary pressures to varying degrees, it’s no wonder we see the after-effects of these processes reflected in a dazzling variety of morphologies in the local Universe. I will focus on just one evolutionary driver: stellar bars. After a brief side track into attempting to quantify just how many galaxies in the local Universe are actually discs, I will try to convince you of the importance these structures for driving galaxy secular evolution. Then, we’ll turn the problem on it’s side: with the help of the GECKOS survey, I will discuss the use of peanuts as time capsules, and how we can use Mike’s Snickers hypothesis to understand bars without seeing them. Confused at my cryptic abstract? I will explain all on Wednesday in a jargon-free manner - come and see!

The influence of AGN activity acts to inhibit gas cooling and hence star-formation on scales of hundreds of kpc in the cores of clusters of galaxies. This AGN Feedback regulates the gas accretion rate onto the central black hole creating a balance in which essentially all cluster cores contain a galaxy with a low accretion rate AGN. I will review our understanding of the cold gas in these systems that can be traced down to single clouds.

Figuring out the physical laws and processes responsible for planet formation and for planetary orbital migration, as well as measuring the occurrence rate of biology in the Cosmos are the two main scientific drivers behind exoplanetology. In this seminar I will review recent exoplanet discoveries and the astronomical methods that have been developed to measure their atmospheric properties. I will also describe recent results of my group, that is discovering temperate rocky worlds orbiting the smallest stars of our Galaxy, as well as circumbinary exoplanets.

One of the main factors regulating the evolution of galaxies is their environment. The difference in the integral properties of galaxies in different surroundings is explained by the presence of mechanisms characteristic of dense circumstances, and the vast majority of them are responsible for cold gas content regulation (ram-pressure stripping, tidal interaction). In this talk, I am going to discuss the challenges in defining the environments of the galaxies and show how environments affect galaxy properties in the example of the Virgo cluster. I will pay special attention to the role of filaments in galaxy evolution.

X-ray observations of bright X-ray binary systems provide an opportunity to view physics close to the event horizon of a black hole, but interpreting the high-energy variability and spectrum is fraught with challenges. Despite years of study and increasingly high signal-to-noise and resolution of the data, there remain stark disagreements in the conclusions different teams draw from the same data. One hotly disputed topic is the location of the innermost edge of the accretion disc, and its connection to the spin of the black hole. In this talk, I will describe our recent work taking a Bayesian approach to this problem, with a focus on one particular X-ray binary system observed by both XMM-Newton and NuSTAR. We attempt to make principled use of the (sometimes very good) information about the binary system available from different observation techniques (e.g. parallax distances, jet inclination, primary mass) while trying to be honest about the uncertainty in the models. I will argue that our work accounts for the assumptions and uncertainties involved in this work more honestly than "standard" methods used in the field, although there is plenty of work to be done to improve each step of the approach.

Quasar-driven outflows (i.e. jets and winds) are widely invoked in galaxy formation models in order to reproduce the observed properties of massive galaxies. However, there are still fundamental open questions regarding the origins of these outflows, and their relationship to accretion processes. Signatures of quasar winds are most commonly observed in the restframe UV spectra of z~2 quasars; however, quasar observations at different wavelengths probe structure on different spatial scales, and it is only by bringing together these multiwavelength datasets as part of a holistic analysis that real progress can be made in understanding how quasars are able to influence their host galaxies. I will provide an overview of the various signatures of quasar outflows observed in the UV before folding in multiwavelength data (X-ray and radio) in order to see what we can learn about the origin and driving mechanisms of quasar winds.

Ultraluminous X-ray sources (ULXs) are off-nuclear X-ray sources with luminosities that exceed the Eddington limit for stellar remnant black holes. This implies either the presence of larger, 'intermediate mass' black holes, or systems that have managed to violate their Eddington limits. Prior to the NuSTAR era, black hole accretors were widely assumed, even in the latter scenario. However, in 2014 NuSTAR made the remarkable discovery that one of these systems, M82 X-2, is in fact powered by an accreting, pulsating neutron star (i.e., a pulsar), firmly demonstrating that this is a source radiating at ~100 times Eddington. Much about these systems remains shrouded in mystery: it is not clear how significantly neutron star accretors contribute to the demographics of the overall ULX population, and it is also not understood how these sources are able to radiate at such extreme levels. As of today, roughly half a dozen neutron star ULXs are known, including systems radiating up to 500 times the Eddington limit. I will discuss the current state of this rapidly evolving field.

The Low-Frequency Array (LOFAR) is a pan-European radio telescope whose massive data taking and processing capabilities make it an unprecedented powerful instrument for carrying out the deepest and widest radio surveys at the lowest radio frequencies accessible from the ground. Over the last years we have addressed important issues related to the analysis and calibration of the radio data so that we can now make thermal noise limited maps at low frequencies. The resulting wide and deep maps enable studies of a wide range of scientific topics ranging from (i) shocks in merging clusters, (ii) radio feedback processes, (iii) star formation in distant galaxies and (iv) the most distant radio AGN, close to the epoch of reionisation. In this talk I will first discuss our solutions to the main technical challenges. Secondly, scientific highlights will be given related to these 4 topics.

As the reservoir for star formation, neutral hydrogen (HI) is an important ingredient in the assembly and evolution of galaxies. However, until recently, observations of HI were mostly restricted to z=0. With new radio facilities, including MeerKAT and the SKA, we can observe HI over billions of years of lookback time, incorporating HI into the observational census in a way not previously possible. I will show recent results from a large survey with MeerKAT, which take advantage of the increased sensitivity to probe fainter and more distant galaxies, providing useful benchmarks for simulations and new probes of galaxy environment.

Clusters of galaxies are the most massive gravitationally bound structures in our Universe and form the nodes of the Cosmic Web. In addition to the up to thousands of member galaxies, galaxy clusters are permeated by the hot ionized diffuse plasma of the intracluster medium (ICM), which forms the dominant baryonic component of the cluster. The ICM releases strong X-ray emission due to thermal bremsstrahlung, causing this medium to cool down. As the ICM cools down, it sinks down the gravitational well of the cluster and accretes onto the central galaxy. Here, it fuels the supermassive black hole located in the core of the galaxy, creating an Active Galactic Nucleus (AGN). This AGN subsequently produces two relativistic jets which shoot into the surrounding ICM to re-energize this medium, which prevents a runaway cooling event and moderates star formation. To understand the formation and evolution of galaxy clusters, it is critical to understand this feedback cycle. The LOw Frequency ARray (LOFAR) is one of the world's leading observatories at low radio frequencies. With its pan-European baselines reaching up to 2000 km in length, it is capable of achieving sub-arcsecond angular resolution at frequencies below 200 MHz. Recent developments of the Long Baseline Working Group have enabled the calibration of these baselines, unlocking the highest resolutions (~0.3 arcseconds) attainable with LOFAR. This has provided an unparalleled view of the radio sky, enabling a wide variety of research for the first time. In particular, the combination of high angular resolutions and excellent sensitivity at low frequencies is ideal for imaging active galactic nuclei and their jetted outflows. In this talk, I will present a brief overview of the ongoing technical work with the calibration of LOFAR followed by a variety of recent results, and I will finish with a brief outlook on LOFAR's future following the upcoming upgrade.

Since its launch in December 2021, the James Webb Space Telescope has begun to deliver on its promise of revolutionising our understanding of the first billion years of cosmic history. In this seminar I will review the progress that has been made in understanding the earliest stages of massive galaxy formation, from the first seeds at z=12-14, through to the first massive objects and luminous AGN at z~10, and the first quiescent systems at z~5.

Constraining the key drivers of cosmic reionization - a major phase transition in the Universe’s lifetime when the intergalactic medium (IGM) transformed from neutral to completely ionized - is a major challenge in astrophysics today. Solving this puzzle requires the knowledge of the number density of galaxies or AGN in the early Universe, the ionizing photon production rates from these sources, and crucially, the escape fraction of these photons that leak into the IGM driving reionization. HST has provided incredible insights into these key parameters over the last decades, and the successful deployment of JWST has ushered in a new era in the detailed study of high redshift galaxies and reionization, opening a new observational frontier. In this talk, I will present the latest results measuring the ionizing photon production and escape from galaxies at high redshifts, including some of the newest results from the JWST GTO, ERS and Cycle 1 programmes. I will also briefly touch upon the role played by exotic systems such as X-ray binaries, as well as AGN in massive galaxies in the early Universe towards reionization. I will conclude by discussing what the field is most looking forward to from more JWST data in the coming months.

The exploding capabilities of new radio observatories such as LOFAR provide great opportunities for studying star forming galaxies beyond the local universe. Recent studies have produced calibrations for estimating star formation rates of distant galaxies based on their radio luminosity, including an unexpected dependence on stellar mass. In this talk, I will outline some ongoing efforts to investigate this surprising result, including (i) determining the extent to which energy-balance SED fitting codes can produce reliable estimates of galaxy physical properties, leveraging simulations where the true properties of the galaxies being modelled are known, and (ii) leveraging a non-parametric method alongside SED fitting and SDSS spectroscopy to independently determine the importance of stellar mass on the SFR-radio luminosity relation. I’ll finish by showing some new results from WEAVE -- the new spectroscopic facility on the William Herschel Telescope -- and describing the WEAVE-LOFAR survey which will deliver more than a million spectra of 150MHz-selected sources over the next five years.

A group discussion on the benefits/pitfalls of using AI in research, focusing on tools like ChatGPT, GitHub Copilot, ... which might help (or hinder!) tasks like writing code or text. I'll put together a few slides to get us going, but it'd be great if people could think about any tools or examples they'd like to talk about, or let me know of any applications they think could be interesting to discuss.

The WEAVE-LOFAR survey will imminently be coming online to unlock the immense potential of sources uncovered by The International LOFAR Telescope, which is opening new parameter space in the low-frequency radio sky. In particular, the LOFAR Two Metre Sky Survey (LoTSS) is surveying the entire northern sky at 150MHz to a depth of ~100 micro Jy, already providing a sample of > 4 million extragalactic radio sources. By providing > 1 million optical spectra for these radio-selected objects, the WEAVE-LOFAR survey will gather statistical samples of both extreme quasars in the early Universe, and 'typical' star-forming galaxies across vast swathes of cosmic time. I will discuss our preparation to harness the massively-multiplexed spectroscopic facility WEAVE, by developing a probabilistic spectroscopic classification method to identify the dominant powering mechanism of LOFAR sources, and refining survey strategy to efficiently observe targets in the deepest tier of WEAVE-LOFAR. Ul timately , WEAVE-LOFAR will be able to distinguish between star-formation and AGN, accretion modes in AGN, and enable us to understand the complex interplay between star formation and accretion from z~7 to the present day.

Measuring the abundance and physical properties of high-redshift galaxies is crucial to understand and constrain the earliest stages of galaxy formation and evolution, including the formation of the first stars and black holes. The first galaxies are a sensitive probe for a range of baryonic processes (gas cooling and energetic feedback from stars and black holes), structure formation and the nature of dark matter. In this talk, I will present new results from JWST on the star-formation and morhpolgoical properties of the earliest galaxies known to us. Specifically, I will introduce the JWST Advanced Deep Extragalactic Survey (JADES), which is the most extensive programme of the first few years of JWST with over 800 hours of observing time. By combining imaging from NIRCam and spectroscopy from NIRSpec, I will show how can find the very first galaxies and characterise their primeval properties.

Understanding the physical processes governing the assembly and growth of galaxies remains one of the great challenges of modern astrophysics. Among the most sensitive observational probes of these processes are galaxy chemical abundances, which are governed by the interplay between star-formation, gas accretion and galactic outflows and are therefore sensitive to the full ‘baryon cycle’. To date, most of our abundance estimates at early cosmic epochs have been limited to gas-phase oxygen abundances measured from rest-frame optical spectra. However, recent advances in the analysis of deep rest-frame FUV spectra have begun yield robust stellar iron abundances, enabling the analysis of detailed abundance ratios, and providing a crucial link to galactic archaeology results in the local Universe. In this talk, I will present the latest results the oxygen and iron abundance of galaxies at cosmic noon and discuss the crucial constraints these measurements place on our understanding of the growth and evolution of galaxies.

The evolution of satellite galaxies is strongly impacted by their environment through various interaction pathways. I will present two projects that aim at understanding the response of satellite galaxies to their host environment, the first studying the impact of the host's merger and assembly history and the second studying ram-pressure stripped `jellyfish' galaxies and their star-formation. Mergers play a significant role in determining several properties of central galaxies, including morphology and star-formation histories, and may also impact the properties of their satellite populations. Using the VINTERGATAN-GM suite of zoom-in hydrodynamical simulations of MW-mass systems, we investigate the impact of a central's merger history on its system of satellites. The suite simulates five realizations of a halo with 'Genetic Modifications' applied to a $z \approx 2$ merger from the fiducial run but resulting in the same halo mass at $z=0$. We show that the merger has a significant impact on the satellite abundances and mass functions for $\sim 2-4$ Gyr after the merger, but this impact is largely erased by $z=0$. The modifications made to the target merger are found to alter multiple other mergers in order to compensate for the mass contributed by the target merger, not only by altering the masses of the central galaxies in the secondary systems, but also through the sate llites they bring along. Our results suggest that diverse merger histories may be a significant source of scatter when reconstructing the host's dynamical properties from its satellite population. I will also describe the Cosmological Jellyfish project, a citizen science project aimed at identifying `jellyfish' galaxies, i.e. galaxies showing signs of ram-pressure stripping (RPS), within the IllustrisTNG suite of cosmological MHD simulations, across several epochs and within a wide range of environments. This dataset allows us to explore the onset and timescale over which RPS occurs and how it impacts the gas content and star-formation within the galaxies affected by it. We show that in the IllustrisTNG model, jellyfish galaxies do not show enhanced star-formation rates at the population level as has been proposed by some observations, but that individual jellyfish galaxies do show bursts of star-formation during pericentric passages.

In this talk I will first present a new automated method based on deep neural networks to detect clumps in galaxy images. I will show that the method is both faster and more sensitive than previous published approaches. I will then show how we use the new method to perform for the first time a systematic detection of clumps in rest-frame optical in a complete sample of ~1,500 star forming galaxies with 1<z<3 in the CANDELS survey and derive clump stellar masses through Bayesian SED fitting. The clump stellar mass functions follow a power-law with a slope of alpha=-1 to -1.5 down to the completeness limit (10^{8.5} solar masses). We find that between 20-40% of star-forming galaxies contain at least one massive off-centered clump but only ~5% of the total galaxy stellar mass is in massive clumps. I will finally show the results of a comparison with forward modeled zoom-in cosmological simulations in which most clumps are formed in-situ through gravitational instabilities. We show that observational effects have a dramatic impact on the derived clump stellar mass functions by overestimating the clump mass up to a factor of 10, which highlights the importance of fair and direct comparisons between observations and simulations and the limitations of current HST data to study the resolved structure of distant galaxies. When all the observational effects are taken into account, we show that the simulations explored in this work overall reproduce the observed clump abundances and clumpy fractions. This good agreement suggests that most of the observed clumps are formed in-situ. I will conclude by explaining how future detailed and consistent comparisons of clump properties - especially observed with JWST - with other simulated samples have the potential to put additional statistical constraints on feedback mechanisms.

Space-based slitless spectroscopy capabilities on-board the Hubble Space Telescope have made it possible for us to conduct spatially-resolved studies of star formation in high redshift galaxies for the first time. The future is truly slitless, with the James Webb Space Telescope and the Nancy Grace Roman Space Telescope vastly improving and capitalizing on the scientific gains we will make with this mode of observation. I will begin by demonstrating how spatially resolved studies with the Hubble Space Telescope have allowed us to determine which galaxy size growth mechanisms dominate and how the quiescent (not forming stars) population of galaxies builds up with redshift. Subsequently, I will unveil the first spatially resolved H-Alpha emission line maps of cluster galaxies at z~1 from the GCLASS survey, made possible with the Wide Field Camera 3 G141 grism on-board the Hubble Space Telescope, revealing what they have taught us about the shutdown of star formation in galaxy clusters at this crucial epoch in the history of cosmic star formation. I will end by presenting deep spatially resolved H-Alpha emission line maps of CANDELS galaxies at z~0.5 from the CLEAR survey, made possible with the Wide Field Camera 3 G102 grism on-board the Hubble Space Telescope, and what these have unveiled on galaxy size growth via star formation at intermediate redshifts. By synthesizing the few existing spatially-resolved studies of High-Redshift Galaxies between 0.5<z<1.7 we now have, I will provide the first results on how star formation propagates spatially in galaxies over time.

Reionization marks the time at which the first stars gradually reionized the Intergalactic Medium (IGM) and the Universe transitioned from highly neutral opaque to a highly ionized-transparent state. Many ongoing and upcoming surveys, such as the Low Frequency Array (LOFAR), the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometer Array (SKA), are devoted to detecting reionization on large scales in the near future. In this talk, I will present two ongoing projects targeting two different but closely related topics. The first part will focus on answering the question: does detailed astrophysics matter to model reionization on large scales? We here examine the impact of using realistic ionizing sources as identified within the state-of-the-art cosmological hydrodynamic simulations, namely Simba, on modelling reionization on cosmological scales, and compare results with the traditional simplified models of reionization. The second part will focus on answering another important question: how to extract the maximum amount of information from future reionization surveys? In this part, we assess the viability of using normalizing flows to generate HI maps conditioned on a set of astrophysical and cosmological parameters from the CAMELS simulations. We show how this method can be used to constrain parameters based on 2D mock maps, as an attempt to go beyond the power spectrum.

Residing at the vertices of this Cosmic Web, clusters grow by steady accretion of matter from the surroundings, as well as by discrete mergers with nearby groups and clusters. Supported by simulations, this scenario regarding the total mass content and distribution in filaments and clusters remains largely untested. While combining gravitational lensing regimes to map the total mass with multi-wavelength imaging and spectroscopy of clusters and their galaxies, one can thus study the dynamical scenarios in place within these objects, trace the substructures engaged in these processes, and constrain evolution and formation theories. I will present the latest results our team obtained combining VLT/MUSE and HST observations, and conclude with a quick overview of the BUFFALO survey.

It has been demonstrated that strong gravitational lensing is one of the most promising methods to distinguish between CDM and alternative dark matter models, through the detection of low-mass dark haloes and subhaloes. Using simulated observations, we quantify the data sensitivity in detail and calculate forecasts for HST, Keck and ALMA observations. I will discuss what is the status of the field and the current dark matter constraints in general, and in particular present the results from my latest paper, which is focused on a comparison between these simulated observations, real data and the halo and subhalo mass function obtained from numerical simulations in CDM and WDM models.

Over 20 years ago, a bright quasar became the first astronomical object detected less than one billion years after the Big Bang. The push for the precision study of high-redshift quasars has culminated in the XQR-30 survey: a collaboration of 44 scientists across 13 institutes, and the largest program yet awarded using the X-Shooter instrument. By obtaining high-quality optical+NIR spectroscopy of 30 quasars at z>~6, XQR-30 is providing both quantitatively and qualitatively new insights into the early Universe. In this talk, I will present the first set of XQR-30 results, which focus on the origin of the first supermassive black holes powering quasars as well as the timing and sources of the epoch of hydrogen reionisation.

Understanding the physical processes responsible for ceasing star formation in galaxies is one of the most important unresolved questions in the field of galaxy evolution. Over the past two decades multiple mechanisms were suggested as potential drivers of the transition between the star-forming and quiescent galaxy categories, referred to as galaxy ‘quenching’. In this talk I will present the results of our recent study, in which we combine machine learning with partial correlation analysis to determine which among the three potential quenching mechanisms: supernova feedback, halo shock heating or AGN feedback are most likely responsible for bringing star formation to a halt in massive, central galaxies. To this end we bridge the gap between theory and observation by extracting theoretical predictions from three state-of-the-art cosmological simulations – EAGLE, Illustris and IllustrisTNG and comparing them with the Sloan Digital Sky Survey (SDSS) observations. We find that the supermassive black hole mass (MBH) is the most powerful parameter in determining whether a galaxy is star-forming or quenched across all datasets. Remarkably, this result is true for all different implementations of AGN feedback in the simulations and is met overwhelmingly well in the SDSS, where we infer MBH from a variety of calibrations for ~230 000 local galaxies. In this talk I will share our results together with our methodology to make a convincing case for star formation being quenched by AGN in massive, central galaxies.

The Epoch of Reionization (EoR) signals the end of the Dark Ages of the Universe and the birth of the first stars. The aim for the current generation telescopes is to make the first statistical detection of this epoch. The foregrounds cover the cosmological data by several orders of magnitude however, and their removal remains a significant challenge. I will speak broadly about the foreground mitigation techniques currently being used with EoR data, with a focus on blind source separation techniques, and discuss whether we have seen a first detection by EDGES, after 8 years of searching.

Cosmological simulations provide an alternative way of probing populations of low-surface-brightness (LSB) populations and features, which make up the majority of galaxies in the Universe and constitute a majority of their visual footprint respectively. As such, the LSB regime is an important new frontier for the study of galaxy assembly as well as more fundamental questions in cosmology, but remains poorly understood in a statistical sense. Based on results from state-of-the-art simulations, I will discuss future prospects for The Rubin Observatory, which is optimised to deliver fast, wide field-of-view imaging and which will enable deep and unbiased observations over the 18,000 square degrees of the Legacy Survey of Space and Time (LSST), resulting in samples of potentially of millions of dwarf galaxies and massive galaxies undergoing tidal interactions. i will also discuss the expected nature, frequency and visibility of tidal features and debris across a range of environments and stellar masses as well as their reliability as an indicator of galaxy accretion histories including how observational biases such as projection effects, the point-spread-function and survey depth may affect the proper characterisation and measurement of tidal features.

The co-evolution of galaxies and their supermassive black holes (SMBHs) via mergers is a long-held paradigm that has recently been overturned. With a sample of `bulgeless’ disk-dominated galaxies Simmons, Smethurst & Lintott (2017) showed that in the absence of mergers, SMBHs can grow to 10^9 solar masses. A follow up study by Martin et al. (2018) found that in simulations, 65% of all the matter contained in SMBHs at z~0 was acquired through non-merger processes. We now present detailed KCWI IFU observations of the [OIII] 5007 Å component for 4 of these `bulgeless’ disk-dominated galaxies hosting luminous, unobscured AGN with spectrally confirmed blue shifted outflows, presumed to be powered by the AGN itself. These massive galaxies’ formation histories are dominated by non-merger secular processes and thus provide a unique opportunity to study how inflows from secular processes fuel significant growth of black holes in the absence of significant mergers. We calculate outflow rates for these AGN in the range 0.12 − 0.7 M_sun/yr, with velocities of 675 − 1710 km/s, large maximum radial extents of 0.6 − 2.4 kpc, and SMBH accretion rates of 0.02 − 0.07 M_sun/yr. We find that the outflow rates, kinematics, and energy injection rates are typical of the wider population of low-redshift AGN, and have velocities that exceed the galaxy escape velocity by a factor of ~30, suggesting that these outflows will have a substantial impact on their galaxies through AGN feedback. This has interesting implications: if both merger-driven and non-merger-driven SMBH growth lead to co-evolution, this suggests that co-evolution is regulated by feedback in both scenarios.

Supermassive black holes seem to be ubiquitous in galaxy nuclei, and several large-scale galaxy properties have been found to scale with black hole mass, giving rise to the idea that galaxies and their black holes co-evolve. There are only a few techniques that can directly constrain the mass of a black hole through its gravitational influence on luminous matter, of which the most commonly used are reverberation mapping and stellar or gas dynamical modeling. These techniques have been applied to a modest number of black holes, with the vast majority of black hole masses in the literature instead being estimates derived from scaling relationships that are based on direct mass measurements. To date, however, there are only a handful of black holes with masses that have been constrained through multiple techniques because of the disparate technical requirements. In AGNs, the situation is even worse because active galaxies are rare and most are too far away to allow the spatial resolution needed for dynamical modeling. I will describe our ongoing project to directly compare black hole masses from reverberation mapping and stellar dynamical modeling in the nearest active galaxies, including our upcoming JWST Early Release Science program. Both reverberation mapping and stellar dynamical modeling are time- and resource-intensive techniques and the number of galaxies we can study with both techniques is small, but the results will help uncover potential biases in these direct mass techniques and illuminate any differences in the black hole mass scales that are applied locally versus at cosmological distances.

In this talk I will discuss how stars and globular clusters (GCs) allow us to trace the assembly of galaxies and their dark matter (DM) haloes, and how these constrain the complex physics of galaxy formation. I will use examples from three studies: In the first, I will describe how studying the phase-space distribution of the MW GCs using Gaia and the E-MOSAICS simulations provides a detailed quantitative picture of the formation of our galaxy. In the second example, I will show how the unusual GC populations in galaxies like the infamous NGC1052-DF2 and DF4 can provide a snapshot of their galactic progenitors at cosmic noon. For these objects, a simple model of star cluster formation points to an extremely dense birth environment and strong structural evolution, providing clues of the effect of clustered star formation on galaxy evolution. I will conclude with a follow-up study of the impact of clustered star formation on galaxy structure that provides clues about the origin of ultra-diffuse galaxies (UDGs), which are difficult to explain in the current paradigm of galaxy formation. I will show how anchoring an analytical model on galaxy scaling relations and numerical simulations predicts the emergence of UDGs that lack DM driven by clustered feedback from young GCs

There is a tight connection between the growth of galaxies and the supermassive black hole (SMBH) at their centres which indicates that the central SMBH plays a significant role in the evolution of its host. In particular, jets emitted from actively accreting SMBHs or radio loud active galactic nuclei (RLAGN) are thought to be a key role-player in the quenching of massive galaxies. While theoretical models have become more useful in understanding the role of RLAGN in galaxy evolution, the processes describing the accretion and feedback mechanisms of these objects, however, are still poorly defined. The SIMBA suite of cosmological simulations is unique in that it models the growth of supermassive black holes via a two mode sub-resolution prescription and includes physically motivated feedback processes. Using SIMBA we can provide a simple approach to defining two sub-classes of RLAGN, namely high- and low excitation radio galaxies (HERGs and LERGs), and investigate the differences in their global and environmental properties. I will present results of the properties of radio galaxies in SIMBA and briefly introduce MIGHTEE, an SKA precursor survey, which aims to probe the accretion and feedback processes of AGN and star formation out to cosmic noon. Additionally I will present a brief comparison of SIMBA with preliminary results of the MIGHTEE radio galaxy population and detail ongoing plans to incorporate high resolution LOFAR observations and semi-analytic models (SAMs) to disentangle the physical mechanisms defining radio emission from star formation and black hole accretion processes.

The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and morphologies). Here we show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. We predict that ~30% of massive central galaxies (with at least 1e11 solar masses in stars) harbour at least one dark- matter-deficient satellite (with 1e8–1e9 solar masses in stars). This distinctive class of galaxies provides an additional layer in our understanding of the role of interactions in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.

The nature of the first galaxies driving the reionisation of the intergalactic medium (IGM) and their imprint in the ionisation state of the intergalactic hydrogen gas remain outstanding questions in current astrophysics. With the advent of the James Webb Space Telescope (JWST), the Nancy Grace Roman Space Telescope (Roman), and the Square Kilometre Array (SKA), a vast amount of data will be collected that will revolutionise our understanding of the first galaxies. The number of detected early galaxies will increase greatly, and the 21cm signal from the neutral hydrogen in the IGM will probe the ionised regions continuously growing around the first galaxies in time and space. Semi-analytic models as well as semi-numerical and numerical simulations provide a great avenue to understand the characteristic signatures of galactic processes in these forthcoming galaxy and 21cm signal (IGM) observations during the Epoch of Reionisation. In this context we have developed the Astraeus framework. Astraeus is one of the largest (230 Mpc box) and highly resolved (DM resolution mass of 10^6.9 solar masses) simulations that couple a semi-analytic model of early galaxy evolution with a semi-numerical reionisation scheme self-consistently. I will introduce this model and use it to explain how radiative feedback from reionisation and the escape fraction of HI ionising photons from galaxies shape the galaxy population driving the reionisation of the IGM. Moreover, I will discuss how galaxy and 21cm signal observations can help us to constrain the ionising nature of these first galaxies and the reionisation process.

Cosmic Dawn and the Epoch of Reionization (EoR) are some of the least explored stages of cosmic history. The faint 21-cm signal of hydrogen atoms in the intergalactic medium provides a unique way to probe these epochs by constraining thermal and ionization history of the Universe. Once this signal is robustly measured, it will inform us about the early populations of stars, galaxies and black holes. In my talk I will discuss the recent advances in the field of 21-cm cosmology.

Massive elliptical galaxies continue to pose a number of puzzles. The stars harboured in their innermost regions, at least, were most likely formed in situ, in intense starbursts at early epochs. Their stellar populations have high metallicities and element abundance ratios unlike any Milky Way stars used to calibrate evolutionary synthesis models. They show unusual features such as the ultraviolet excess, from low-mass undergoing non-standard post-main-sequence evolution. And they exhibit a characteristic spectral signature that seems to require an initial mass function — yet the corresponding excess stellar mass is not detected in gravitational lensing, for the most robustly constrained systems. In this perplexing context, we need to develop new techniques to probe the stellar content in ellipticals, and to test some of the most uncertain aspects of today’s population synthesis models. In this talk, I will describe a method which exploits the Poisson variation in the number of giant stars contributing to each pixel in integral-field spectroscopy. While related to the “surface brightness fluctuations" technique in imaging observations, our new formulation accesses richer information, and more efficiently, by pooling information across the entire data cube. I will outline the principles of the method and show practical results from a first application to observations of Centaurus A with MUSE used its high-resolution adaptive optics mode. I will close with some discussion of prospects for extending this method to the cores of “true” elliptical galaxies with future instrumentation

The last decade has seen an explosion in our knowledge of extra-solar planets, and we now know of thousands of exoplanet systems with an extraordinary range of properties. These planets formed in cold discs of dust and gas around young, newly-formed stars, and in recent years we have also seen major advances in our observations of such discs. In this talk I will discuss how these protoplanetary discs shape the formation and evolution of planetary systems, and how planets and other processes can give rise to observable structures in their parent discs. I will present new models of protoplanetary disc winds, and show how forbidden emission lines can be used to measure the properties of these winds and their effects on disc evolution. I will also present new models of planet-disc interactions, and look in particular at the dynamics and observable signatures of planets on inclined orbits. Finally I will discuss how we can apply these results more broadly, and what we can hope to learn in the coming years.

Galaxy clusters are connected at their peripheries to the large scale structures by cosmic filaments that funnel accreting material. These filamentary structures are studied to investigate both environment-driven galaxy evolution, out-of-equilibrium gas physics, and structure formation processes. In this presentation, I will first explore how the cosmic filaments connected to clusters are influencing the dynamical state and the formation history of galaxy clusters, by using simulated clusters from IllustrisTNG simulation. Secondly, we will discuss how the gas is distributed around these simulated galaxy clusters, from their hot plasma inside clusters, up to the warm hot inter-galactic medium which is slowly infalling along cosmic filaments. Finally, the galaxy distribution around clusters is investigated in large photometric galaxy catalogues around 6400 SDSS clusters (0.1< z <0.3). This statistical study suggests that infalling galaxies stop to forming stars inside filaments before entering into clusters.

Thanks to upcoming experiments such as the SKA and HERA, large-scale observations of the Epoch of Reionisation (EoR) are now within reach. Developing simulations that can produce reliable forecasts for these world-class instruments is both vital and extremely challenging, due to their huge computational requirements. Semi-numerical models of the EoR, due to their unmatched speed, are generally the technique of choice when it comes to simulating EoR data on such large scales. They are, however, prone to issues relating to photon conservation, which have been shown to have a tangible effect on the predicted power spectra. In this talk, I will introduce ARTIST, a radiative transfer method which aims to resolve this conservation issue without significantly compromising the efficiency of the simulation. Such improvements represent an important step towards understanding the EoR and maximising the amount we can learn about cosmology from EoR observations.

Astronomy is sometimes regarded as the mother of all sciences, dating from when the first humans tried to understand the starry night sky and its relationship with our world. Every civilisation has developed its own cosmological models and world representation based on the observation of celestial bodies.Therefore, astronomy is also deeply rooted in Africa. Today, several African countries have operating or planned optical observatories, and the Square Kilometer Array (SKA), the largest astronomical installation so far, is underway with crucial nodes in Africa. In this talk, I will talk about some projects and initiatives, initiated within the International Astronomical Union and/or by its members, focused on the development of astronomy in Africa. I will also talk about about some cultural astronomy and STE(A)M* education projects on the African continent I have been involved in.

The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling large data volumes and automating many tasks traditionally done by human scientists. In this talk, I will discuss how machine learning for anomaly detection can help automate the process of locating unusual astronomical objects in large datasets thus enabling new cosmic discoveries.

I will present results from a recent/ongoing investigation of galaxy population properties in the most distant galaxy clusters identified in the Sunyaev-Zel'dovich SPT-SZ survey. SPT-SZ identified clusters over 2500 square degrees with an approximately redshift-independent mass threshold of ~4e+14Msun from z~0.2 out to the highest redshifts where such structures exist. We have focused on the highest-redshift tail of this cluster sample, studying five systems at 1.4<~z<~1.7 among the rarest, most massive clusters known at these redshifts. Because of its selection independent of galaxy properties, this sample is particularly well suited for galaxy evolution investigations. In the context of the many studies of galaxy evolution in distant clusters, I will present our results based on dedicated HST and Spitzer follow-up observations of this cluster sample, focusing on environmental quenching and structural evolution of galaxies in the first massive cluster environments.

Galaxies do not evolve in isolation, but are sensitive to their local environments. Satellites in groups and clusters do not accrete fresh gas efficiently, and are subject to additional physical processes such as ram pressure from the intra-group/cluster medium, tidal stripping in the host potential, impulsive encounters with other satellites, etc. While it is clear that all these processes operate at some level, which are most important in setting the evolution of satellites as a function of their mass, their orbits, and the mass of their host is an ongoing area of research. I will present a new analysis of SDSS and ALFALFA survey data. I use a library of satellite orbits drawn from an N-body simulation to probabilistically assign satellites to orbits based on their observed offsets from their hosts in position and velocity. I then use these data to constrain a simple analytic model describing the relationship between satellites' orbital and star formation (or gas content) histories. This reveals the sequential impact of the host environment, first on the gas supply, then on the star formation rate.

Neutral hydrogen in the Intergalactic Medium produces a collection of Lya absorptions, called the Lya forest, seen in the spectra of background objects. According to the common paradigm, neutral hydrogen in the IGM evolves from primordial density fluctuations in a low density and photo-ionized environment. It therefore acts as a direct tracer of Dark Matter (DM). However, it also implies that temperature and density are tightly coupled, giving rise to degeneracies between parameters describing either cosmology or the IGM thermal history. The Lya forest 1D power spectrum (P1D) is sensitive to clustering on small scales, and as such to the smoothing scale of relativistic particles. It has been used to put the strongest constraints on the sum of the neutrino masses. To infer cosmological constraints and to test our models at the percent level accuracy, the measurements need to be compared to state-of-the-art hydrodynamical simulations. We also need to refine our understanding of the impact of galactic feedbacks on the IGM temperature.

MIGHTEE is a galaxy evolution survey currently underway with the MeerKAT radio telescope. Once complete, the survey will cover 20 square degrees in four fields to a depth of ~1 uJy rms/beam at 1.2 GHz, providing a unique combination of depth and breath. Crucially, the MIGHTEE fields have excellent multi-wavelength coverage, enabling a full census of galaxy properties. I will provide an overview of the early-science results from the radio continuum part of the survey, focussing on the role radio-loud AGN play in galaxy evolution.

Modern astronomical studies have identified filaments at all scales, from cosmological Mpc-like sizes down to the small sub-pc features prior the formation of individual stars. The presence of these ubiquitous filamentary structures reveals the intrinsic multiscale and anisotropic nature of the physical mechanisms governing our Universe. However, the internal properties of these filaments dramatically change depending on their scale, environment, and origin. During my talk I will introduce a local (parsec-like) perspective on the study of filaments and star formation in our own Galaxy. I will discuss the formation, stability, and evolutionary properties of filamentary gas structures as well as some of the techniques used for their identification and analysis. Moreover, I will introduce some of the later results and challenges on the study of Milky Way filaments using state-of-the-art radiotelescopes such as ALMA. By discussing their similarities and differences, as well as the alternative approaches used for their study, my aim is to establish a direct dialogue between researchers working on filaments at different scales, from Cosmology to Galactic works.

It has been claimed for decades that almost all galaxies in the local Universe host at their centre a supermassive black hole (SMBH) the mass of which appears to be tightly correlated with the stellar mass and the random motion ("velocity dispersion", sigma) of the stars in the host galaxy. In this talk I will first review the state of the art in this field. I will then highlight that significant biases affect local black hole-galaxy correlations. I will specifically show that the majority of quiescent early-type galaxies with central black hole dynamical mass estimates have significantly higher velocity dispersions than local typical galaxies of similar stellar mass. Through aimed Monte Carlo simulations, residual analysis, and the comparison with latest AGN clustering measurements, I will then illustrate that present data sets of active and quiescent galaxies strongly favour on average lower SMBH masses than previously thought, and point to velocity dispersion as more ``fundamental'' than galaxy stellar mass, galaxy size or Sérsic index. I will then move on discussing the main implications of these findings, in particular: 1) The implied black hole radiative efficiencies and obscured fractions; 2) the consequences on feedback from active black holes and SMBH binary gravitational waves; 3) the connection to cosmological models that rely on velocity dispersion, rather than stellar mass, as main driver of black hole growth.

The Planck space mission has released exquisite observations of the early universe, providing the strongest evidence yet that the universe we live in is very dark indeed. Its precise results show that our universe is composed of 27% dark matter and 68% dark energy, while less than 5% is made up of the baryonic material that we are familiar with on Earth. With their long-standing quest to make these precision measurements essentially now concluded, cosmologists are rapidly turning their attention to a much bigger and further-reaching question: what is the exact nature of this dark universe? I will introduce the Kilo-Degree Survey (KiDS), which we’ve used to map out the invisible dark matter and confront theories on the origins of dark energy. Interestingly the increasing precision that KiDS has recently reported reveals a tension with Planck’s initial conclusions. Is this is a sign that new data challenges lie ahead, or is it our first hint that the universe is truely exotic and that in order to understand the dark universe we will need some new physics that will forever change our cosmic view.

The telescope has been around for more than 400 years and yet most people have never had the chance to look through one. We take our portable computerised telescope to schools and villages and provide guided tours of the night skies to school kids, tourists and members of the public. We also take our 8 meter mobile planetarium around and have recently completed our bamboo dome in the heart of Nairobi. Our talk will focus on this journey and our future plans.

Current and future cosmological surveys (SDSS-IV/eBOSS, DESI, Euclid) are targeting star forming galaxies emission line galaxies at z~1. These galaxies are dominated by [OII] emitters when the selection is done using optical instruments. This talk will start with an overview of the different techniques to study the formation and evolution of galaxies computationally to then focus on the modelling of star forming emission line galaxies (ELGs). Using a state-of-the-art model of galaxy formation and evolution we explore the global properties of [OII] emitters, including their large scale environment. Model galaxies are selected with cuts in different properties such that the samples can be directly compared with a range of both narrow and wide observational surveys: DEEP2, VVDS, eBOSS and DESI. The selected [OII] emitters are hosted by haloes with halo masses above 10^10.3 Msun/h, with ~90% of them being central star-forming galaxies. The predicted mean halo occupation distributions of [OII] emitters has a shape typical of that inferred for star-forming galaxies, with the contribution from central galaxies being far from the canonical step function. The mean halo occupation distribution for central [OII] emitters can be described as the sum of an asymmetric Gaussian for disks and a step function for spheroids, which plateaus below unity. The large scale environment of model galaxies is obtained for fixed number density samples, using a velocity-shear-tensor and a tidal-tensor algorithms. About half of the fixed number density ELGs live in filaments, following the distribution of SFR selected galaxies with the same number density, and a third in cosmic sheets. SFR cut selected ELGs and general galaxies with equal number density, have the same large scale bias but their clustering below separations of 1Mpc/h are different. Although as a first approximation the samples that will be targeted by DESI, 4MOST, MSE, etc. are simply star forming galaxies, the model ELGs do trace a slightly different large scale environment.

The star formation histories of galaxies have the potential to provide strong constraints on the most important processes driving galaxy evolution and quenching. However, obtaining reliable measurements from observational data is fraught with difficulties. In this talk I will introduce Bagpipes, a new public Python code that allows users to build sophisticated model galaxy spectra and fit these to combinations of spectroscopic and photometric observational data using cutting edge Bayesian statistical techniques. I will demonstrate the use of this method to analyse a sample of ultra-deep spectra for massive quiescent galaxies at 1.0 < z < 1.3 from VANDELS, investigating quenching physics at high redshift by constraining the SFHs of these objects and the stellar mass vs stellar age relationship. Finally I will discuss ongoing efforts to identify the first massive quiescent galaxies at z > 3, and what these objects can tell us about massive galaxy formation during the first billion years.

SuperWASP, the world's leading ground-based survey for transiting exoplanets, used wide-field robotic telescopes to continuously image the night sky for a decade. As well as detecting ~200 exoplanets, SuperWASP also built up an archive of observations of >30 million bright stars, ideal for studies of stellar variability. This includes stars displaying pulsations or outbursts, as well as eclipsing binary stars and stars displaying rotational modulation. A recent period-search of this archive identified ~1.6 million possible periods in ~750,000 objects, each of which was converted to a light curve. To classify each light curve, we’ve enlisted the help of citizen scientist volunteers in a project called SuperWASP Variable Stars, hosted on the Zooniverse platform. We’re combining the ‘wisdom of the crowd’ with machine learning to classify all ~1.6 million light curves and find unique stellar variables. So far, over 300 new variables have been identified, including extreme stellar binaries. In this talk, I will highlight some of the most exciting results of the project so far, and describe the next steps for the SuperWASP Variable Stars team.

In the first two thirds of the seminar, I will show how the Herschel Space Observatory has given us a radically different perspective on the galaxy population from the traditional optical view. I will argue that the paradigm that galaxies fall in two distinct classes, with some catastrophic 'quenching process' moving a galaxy from one class into another, is wrong. In this part of the seminar, I will also touch on the use of the lensed systems found in the Herschel surveys to investigate galaxy formation. In the last third of the seminar, I will describe a new project we have started to survey the Andromeda Galaxy at submm wavelengths.

I will summarise the results of our recent paper (Delhaize et al., 2021) on the discovery of two giant radio galaxies (GRGs) in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey. GRGs are the largest single objects in the Universe and are relatively rare, with fewer than 850 currently known. Only around 7% of these have sizes greater than 2Mpc, yet we have detected two such objects within a 1 square degree field in MIGHTEE-COSMOS Early Science observations. Only the cores of these GRGs were clearly visible in previous high resolution observations with the VLA. However, the unprecedented surface brightness sensitivity of the new MeerKAT telescope allowed the diffuse emission of the large-scale jets and lobes to be detected for the first time. We calculate a very small probability of finding two or more such GRGs in the field, supporting the hypothesis that the sky density of GRGs is likely much higher than previously thought. This could have important ramifications on our understanding of the AGN duty cycle and the impact of the radio jets in the evolution of the host galaxy. The two GRGs presented here may be the first of a new population to be revealed through surveys like MIGHTEE, which provide exquisite sensitivity to diffuse, extended emission.

Understanding the processes that regulate star formation in galaxies remains at the heart of modern extra-galactic astronomy, and debate continues as to why some galaxies exhibit powerful starbursts whilst others are largely dormant. The key to progress in this arena lies with assembling large, diverse samples of galaxies for which we can measure all of the critical ingredients, such as the current star formation rate (SFR) and gas content. However, it is insufficient to simply measure global galactic quantities, as we know that a given galaxy will manifest considerable internal diversity in its star formation activity. It is therefore essential to study gas and star formation on spatially resolved scales. The ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey combines maps of stellar properties obtained from the MaNGA (optical) integral field unit survey with ALMA CO (1-0) maps on a common kpc-scale grid, in order to tackle questions of star formation in local galaxies. The 46 galaxies in the ALMaQUEST sample span a wide range of SFRs, including both normal star forming galaxies, as well as those both on their way to quenching, and those undergoing starbursts. In this talk, I will present the ALMaQUEST view of understanding the interplay of gas and star formation across this broad galactic landscape.

Global and sub-galactic metallicities provide a key insight into constraining galaxy evolution. In this talk, I will present recent results on the evolution of global and sub-galactic metallicities as revealed by MaNGA and the new L-GALAXIES 2020 semi-analytic model of galaxy evolution (https://ui.adsabs.harvard.edu/abs/2021MNRAS.503.4474Y/abstract). Very efficient direct metal enrichment of the circumgalactic medium by SNe is required in L-GALAXIES 2020 in order to match the gas (Zg) and stellar (Zs) metallicity profiles seen in a sample of 571 MANGA disc galaxies. These more metal-rich outflows do not require increased mass-loading factors, in contrast to some other galaxy evolution models. Importantly, this new L-GALAXIES 2020 model is also able to simultaneously reproduce the observed global mass – metallicity relations for gas and stars at z = 0, their evolution back to z ∼ 2−3, and the metal abundances observed in the intracluster medium, as well as other key galaxy scaling relations. Finally, I will show that massive disc galaxies in L-GALAXIES 2020 have slightly flatter Zg profiles than their lower-mass counterparts, due to more efficient enrichment of their outskirts via inside-out growth and metal-rich accretion. Such a weak, positive correlation between stellar mass and Zg gradient is also seen in MaNGA and MUSE, although below log10(Ms/Msun) ∼ 10.0 this is strongly dependent on the metallicity diagnostic and morphological selection.

How and when the first luminous sources reionized diffuse baryons in the intergalactic medium (IGM) is one of the most fundamental open questions in cosmology. I will first present a summary on our present knowledge on this process and the most promising observational techniques currently used to further investigate it. I will show that even after reionization is complete, its thermal vestiges persist in the IGM to much later times. Therefore, by measuring the thermal state of the IGM from the statistics of the high-z (z~5-6) Lyman-alpha forest, we can place constraints on reionization. I will present results from hydrodynamical simulations that make use of a new method to generate self-consistent inhomogeneous thermal and reionization histories and direct constraints on when HI reionization happened and how much energy per atom was injected into the IGM. Finally, I will show that at even higher redshifts when the Lyalpha forest line saturates it can be possible to use the "metal line forest" to provide constraints on the global neutral hydrogen fraction and metallicity abundance.

Where do stars form and how is their formation regulated across galactic disks are two critical questions for our understanding of the star formation process. High angular observations of nearby galaxies allow us to sample the star formation process across entire galactic disks reaching now regularly the scales of the star-forming units, namely Giant Molecular Clouds (GMCs) and HII regions. Such data provide new insights on the molecular gas reservoir and its role in the star formation process as well as information on the importance of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. I will introduce the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) survey and present a few highlights from the ongoing research of the collaboration.

I will present an overview of my PhD research into star formation in galaxies at high redshift. The SCUBA-2 Cosmology Legacy Survey is a rich dataset, unique in its depth and sky coverage at submillimetre wavelengths and covering a range of well-studied extragalactic survey fields. I have used it as the starting point for three projects looking at the nature of submillimetre galaxies, investigating the following questions: What is the relationship between supermassive black hole growth and star formation in massive galaxies? How do the low-frequency radio properties of star-forming galaxies compare with their submillimetre properties, and what might we infer from their radio spectra? And can cosmological simulations accurately reproduce the observational properties of highly star-forming galaxies? I will discuss my work on these topics, as well as introduce the project that I am now working on at the UK Astronomy Technology Centre, AtLAST - a three year design study making the case for a 50m submillimetre telescope to be built in the 2030s.

One key problem in astrophysics is understanding how and why galaxies stop forming stars. The exact mechanisms that lead to the disruption of the gas supply, the relative importance of different quenching mechanisms, and the timescales involved are still poorly understood. Post-starburst galaxies are an ideal laboratory to study the galaxy transition process as they have undergone a recent, rapid shutdown in star formation. My recent work showed that post-starburst galaxies are not completely devoid of gas, which challenges the rapid quenching mode thought to form the quiescent population. Using wide-area photometric and spectroscopic surveys, I will describe what the stellar, gas, and dust properties of post-starburst galaxies reveal about the processes causing galaxies to transition from star forming to quiescent.

Radio telescopes such as MeerKAT, and in the future SKA, can map the spatial distribution of the low redshift cosmic neutral hydrogen using Intensity Mapping techniques for the 21 cm line. These measurements can unveil the underlying large-scale structure of the Universe and contribute in a fundamental way to constrain cosmological parameters. A key challenge is the subtraction of the bright foregrounds, orders of magnitude stronger than the 21cm signal. It is, therefore, crucial to assess through simulations the performance of foreground cleaning in realistic scenarios, improving both the sky model and the instrument characterization. In this talk, I will present the current status of an Intensity Mapping survey with MeerKAT in single-dish mode. I will also discuss the effort, carried out with the SKA Intensity Mapping Focus Group to construct a realistic mock data cube for both MeeKAT and the SKA, and to test and compare different foreground cleaning methods.

We report results on the kinematics of Milky Way globular clusters based on updated space velocities for nearly the entire globular cluster population. We found that a 3D space with the semi-major axis, the eccentricity and the inclination of the orbit with respect to the Milky Way plane as its axes is helpful in order to dig into the formation of the globular cluster system. We find that globular clusters formed in-situ show a clear correlation between their eccentricities and their orbital inclination in the sense that clusters with large eccentricities also have large inclinations. Accreted globular clusters do not exhibit a relationship between eccentricity and inclination, but span a wide variety of inclinations at eccentricities larger than 0.5. These findings can be interpreted as if globular clusters formed from gas that collapsed radially in the outskirts, with preference for relative high infall angles. As the material reached the rotating forming disc, it became more circular and moved with lower inclination relative to the disc. A half of the globular cluster population was accreted and deposited in orbits covering the entire range of energies from the outer halo to the bulge.

Stars are fossils that retain the history of their host galaxies. At the end of their lives, some explode as supernovae, producing heavy elements that are distributed into the surrounding interstellar gas. New stars that are created from this gas contain the elements that were produced from the previous generations of stars. From the spatial distribution of elements, it is therefore possible to constrain the star formation and chemical enrichment histories of the galaxies. This approach, Galactic Archaeology, has been popularly used for our Milky Way Galaxy. It can also be applied to external galaxies thanks to the recent and future observations with integral field units such as MaNGA and JWST/NIRSpec. My team has been running hydrodynamical simulations from cosmological simulations including detailed chemical enrichment. I will show how well our model reproduces the elemental abundances in the Milky Way, and how the radial distribution of elements depends on the merging history of galaxies and on their environment. I will then propose a new way to constrain the formation timescale of disk galaxies from their CNO abundances for the era of JWST.

Gas accretion onto a supermassive black hole can launch powerful, high-velocity winds and relativistic jets into the host galaxy. Recent discoveries of massive, kpc-scale gas flows show that these winds and jets plough into the surrounding interstellar medium and disrupt and expel cold gas clouds, which would otherwise collapse to form stars. Known as AGN feedback, this is thought to be the essential mechanism slowing massive galaxy growth at late times in the Universe. With the arrival of the Atacama Large Millimeter Array (ALMA), we can now resolve the structure of these cold gas flows to understand how the supermassive black hole's energy is coupled to the host galaxy. I will review observations of a dozen early ALMA targets, which reveal a distribution of morphologies from filamentary to disk-dominated structures. In most systems, half to nearly all of the molecular gas lies in filamentary gas flows which are entrained around radio bubbles inflated by the jet. Uplifted gas will stall and fall back to the galaxy in a circulating flow, which may eventually fuel the black hole. The distribution in morphologies therefore implies slowly evolving molecular structures driven by the episodic activity of the central black hole.

I will present ongoing work investigating the formation of molecular clouds and stellar clusters from galaxy scales to individual clouds. I will first highlight main presults from previous simulations of spiral galaxies which show the formation of giant molecular clouds via self-gravity and cloud-cloud collisions. In these simulations, stellar feedback is found to be important both to limit the star formation rate, and determine the properties of the clouds. I will also show results from recent models of the galaxy M33, which are able to reproduce the observed properties of molecular clouds in that galaxy. I will then move on to smaller scale simulations which are better able to resolve stellar feedback, including ionisation, and stellar clusters. We study the effects of photoionsation and find that unlike isolated cloud type simulations, ionisation fronts traverse from star forming clouds to other material. The ionisation is able to compress this material into denser filaments and clouds, triggering star formation. After an initial stage of triggered star formation, the star formation rate is then reduced compared to the case without any stellar feedback. The ionisation also produces less gravitationally bound clusters compared to without ionisation. Finally I will present some results from simulations of colliding clouds, showing the formation of young massive clusters (YMCs), and highlighting the conditions under which YMCs can be expected to form.

Nuclear star clusters (NSCs) are a common characteristic of dwarf galaxies, particularly higher-mass dwarfs. There are two main scenarios discussed in the literature to explain their formation, in-situ formation and migration, and clues to the formation of an NSC lie in its SFH. However, NSC spectra are contaminated by light of the host galaxy, making it difficult to isolate the stellar populations of the NSC itself. As part of the Next Generation Fornax Survey (NGFS), I am using BUDDI (Bulge-Disc Decomposition of IFU data) to overcome this issue. BUDDI uses information from the entire datacube to create a wavelength-dependent model of each each component within a galaxy, from which one can extract a spectrum representing purely the light from that component.

Chondrites are shrapnel from unmolten planetesimals that arrived on the Earth, intact, after an interplanetary journey from the Asteroid Belt. Often thought of as cosmic sediments, chondrites are made from the dust from which the asteroids, comets, and planets formed, and therefore preserve material from the onset of the Solar System’s rock record. They hold information about when, and how, our Solar System formed. A key constraint on models of Solar System formation is the timing, order, and duration of events in the protoplanetary disc. The two cornerstones of early Solar System chronology — the extinct 26Al→26Mg and the extant 238,235U→206,207Pb chronometers — are powerful tools, but often yield conflicting results. Understanding and resolving these conflicts is key to our understanding of how the first solids formed, and how the Solar System evolved from a disc of gas orbiting a protostar to the clockwork system of planets we see today.

I will present key results from the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM), a high resolution survey of molecular gas in galaxy nuclei. First, I will show that CO can be used to easily and accurately measure the masses of the supermassive black holes lurking at galaxy centres. I will then discuss substantial ongoing efforts to do this, and present many spectacular new ALMA measurements, the latest of which rival the best black hole measurements to date. This opens the way to literally hundreds of measurements across the Hubble sequence (in both active and non-active galaxies) with a unique method. I will also briefly show how the same data allow to study the spatially-resolved properties of the giant molecular clouds in nearly all the galaxies studied. This will yield cloud censuses in non-local galaxies (including early-type galaxies) for the first time, providing a new tool to understand and contrast the star formation efficiency across galaxies. Already, it appears that basic cloud properties are not universal and vary systematically along the Hubble sequence, contrary to long-held assumptions.

With a background in Geospatial Sciences and a recent move towards data analytics and machine learning, my research interests lie somewhere in between these two worlds. After introducing some of the main Geospatial research domains, I will take you through some facets of my PhD, centered around the use of Global Navigation Satellite Systems in the quest for Olympic Gold. I will then cover a number of projects relying on the use of Satellite Imagery and machine learning to automate various tasks from land use mapping, to road quality estimation in developing countries. The final focus will be on vulnerability mapping in Asia, through the automated and large-scale detection of kilns used in brickmaking, an industry largely uncontrolled but suspected to be linked to modern slavery. Finally, I will detail what this domain can learn from other fields, including Astronomy.

I will discuss a few key advancements in our understanding of the cosmic web and its effect on the properties of collapsed objects, such as dark matter haloes and galaxies. The cosmic web represents the intricate pattern seen in the distribution of matter and galaxies in the cosmos. It consists of large nearly-empty voids, separated by tenuous sheets that connect to form prominent filamentary bridges, which, in turn, shape the accretion into galactic- to cluster-mass systems. Similar to halos and galaxies, the web environments come in a diversity of shapes and sizes: from prominent filaments connecting galaxy clusters to tenuous tendrils crisscrossing the cosmic voids. This diversity is easily seen in cosmological simulations, and, recently, with the advent of deep galaxy surveys (e.g. GAMA, upcoming DESI BGS) also in observations. The properties of haloes and galaxies are correlated to their web environment, but to a lesser extent than initially thought. While the mass function of haloes and galaxies varies strongly between web environments, at fixed mass the correlations with the cosmic web are more subtle, as I shall discuss. Some examples include the alignment of halo and galaxy spins with their host filament, and the propensity of galaxies to be redder when closer to filaments. Part of the challenges in describing these correlations come from the fact that filaments have a large diversity and that galaxy properties are sensitive to the nature of their filaments. Future improvements would mean going beyond the simple classification into knots, filaments, and sheets, which, while easy to describe and imagine, contains only a limited amount of physical information

NASA's Chandra X-ray Observatory was launched on 23 July 1999 by the Space Shuttle Columbia. Now celebrating its 20th year of operations, Chandra continues to be an indispensible tool for expanding the frontiers of knowledge throughout astrophysics. Chandra's uniquely high (sub-arcsec) spatial, and spectral resolution have facilitated the deepest (7Ms) image of the X-ray sky, finding it to be dominated by active galaxies, and the highest quality X-ray spectra to date, revealing the dynamic, multi-component structure of material close to the SMBH. I will provide a review of Chandra and its broad scientific impact, before concentrating on Chandra's results on extragalactic science including galaxies, clusters of galaxies, active galaxies and cosmology.

Active galactic nuclei (AGN) are signposts of the luminous growth of supermassive black holes. During this phase, strong winds can impact the formation of new stars in a galaxy. The short lifetime of the AGN phase makes them very rare objects. Moreover, they are often found with varying methods across the electromagnetic spectrum, with very little overlap between the selected galaxy samples. In tandem with the traditional geometrical paradigm that gives rise to the AGN types (obscured versus unobscured), pieces of evidence point towards an evolutionary approach  linking the various AGN populations and also the host galaxy. Upcoming surveys such as Euclid and LSST will offer a significant boost in galaxy and AGN studies due to the unparalleled sample size of billions of detections. Machine-learning techniques are arguably a very efficient approach to selecting AGN,  next to traditional AGN selection methods. Such methods can be trained to identify known classes of objects, but they can also be used for novelty and anomaly detection. I will present recent results and future prospects of machine-learning AGN identification methods in anticipation of Euclid.

The standard model of cosmology is very successful in describing many key observations with only very few parameters and at high significance. However, this phenomenological description of the Universe is no real attempt to understand the true nature of its most dominant components today, dark matter and dark energy. More importantly, tension between theoretical predictions and observations arises when entering the astrophysical realm of dark matter haloes that decoupled from the Hubble flow. The observed mass function of galaxy clusters, the observed density profiles and substructure contents of objects spanning all mass ranges are not quite in line with theoretical predictions. This is why we are most interested in the non-linear regime of structure formation. While for many on-going and planned cosmological surveys this regime is a mere nuisance which needs to be controlled in order to obtain unbiased cosmological parameters, its detailed study is also one of the most promising ways to achieve deeper insight into the mechanisms of structure formation.  In my presentation I will show how we can use gravitational lensing to unveil and study non-linear structure in the sky. I will present novel mass mapping techniques which combine many different probes into a joint reconstruction of the density field. In order to optimally characterise such maps beyond the usual approach of 2-point statistics and 1D parametric density profiles, we deploy a number of machine learning techniques from the field of computer vision, which allow tighter inference on the most degenerate cosmological models. All these techniques are based on the use of modern many-core computational architectures (such as GPUs), which I will also introduce, and which are able to harvest upcoming large data sets efficiently. I will present results from earlier lensing surveys such as CLASH and show our current efforts within the on-going KiDS survey. I will end my presentation with our plans to fully exploit the potential of the upcoming Euclid satellite. 

Accretion discs around rotating black holes are often assumed to be aligned with the black hole spin. Relaxing this assumption by inclining the disc means that the rotation of the black hole is able to affect the disc evolution, leading to previously unexplored structures in the disc. I will present three-dimensional simulations investigating the evolution of such tilted discs at a range of inclinations. In the small inclination case we identify an oscillatory disc profile, in agreement with previous analytical predictions. In the high inclination case we confirm disc breaking and tearing, where the disc is torn in independently precessing rings of gas. I will then consider applications of these structures to observational features, considering the currently unexplained phenomenon of quasi-periodic oscillations. Turning to geometrically thick accretion flows we consider a torus (with a donut shaped profile), such as would form from a tidal disruption event. Simulating a torus in three-dimensions is difficult as they may be unstable to the non-axisymmetric hydrodynamic Papaloizou-Pringle instability. I will present our simulations of an idealised, circularised torus that has similar parameters to a previously simulated tidal disruption remnant and show that i) it is unstable to this instability and ii) this instability is capable of driving angular momentum transfer. Our simulations imply that the initial accretion rate (and hence lightcurve) of tidal disruption events may be constrained by this instability rather than the magneto-rotational instability in the case of extremely weak initial magnetic fields.

Species of animals are disappearing from Earth at a rate not seen since the extinction of the dinosaurs. Protecting biodiversity is vital for a multitude of environmental and societal reasons. To form effective conservation strategy detailed understanding of wildlife populations is needed. However ecosystem knowledge is still commonly based on data gathered through foot surveys. Drones offer a major advantage for ecosystem surveying, animal tracking and monitoring for poachers as they can survey large areas or difficult terrain quickly with minimal disturbance to wildlife. But this comes with its own challenges, such as optimizing observing strategy and analysing the ever increasing quantity of data produced. In a world first collaboration between astronomers and ecologists, we are adapting techniques used in astrophysics to help revolutionise conservation ecology through the use of thermal equipped drones. I will discuss the solutions we are developing and some of our recent successes.

I present STEEL our new STatistical sEmi-Empirical modeL designed to probe the distributions of satellite galaxies in groups and clusters over many epochs. An accurate picture of halo richness over a large redshift range is crucial to our understanding of how hierarchal assembly effects galaxy population statistics. I show how by discarding traditional merger trees in favour of number density functions I am able to resolve ‘rare’ structures simultaneously with the general subhalo population at all redshifts. I show that using only dark matter structure, dynamical friction, and abundance matching a good match to the satellite population can be found over many epochs. Finally I will discuss how using the statistical framework we can test statistics of galaxy populations and galaxy formation models.

Galaxy clusters are dark-matter dominated systems enclosed in a volume that is a high-density microcosm of the rest of the universe. They are the nodes of the Cosmic Web, constantly growing through accretion of matter along filaments and via occasional mergers. With most of the baryons in the form of X-ray emitting plasma, clusters are thus excellent laboratories for probing the physics of the gravitational collapse of dark matter and baryons, for studying the non-gravitational physics that affects their baryonic component, and as cosmological probes. I will revise the present constraints we have on the ICM in the regions approaching the virial radius from our ongoing X-COP project, what are the open questions on the properties of the ICM there, and how we can try to characterize it with our next XMM-Newton Heritage Cluster Project and with the future generation of X-ray (Athena) and radio (SKA) telescopes.

I will give an overview of recent constraints on reionization from Lyman-alpha and 21cm emission/absorption with special emphasis on the implications of the rather large scales (>=50cMpc) of observed large Lyman-alpha opacity fluctuations at z>~5.5 on the timing of reionization and the nature of ionizing sources.

Asymmetric drift is the rotational lag of the stellar component of a galaxy disk with respect to the circular speed defined by its gravitational potential.  The underlying physical mechanism is that gas efficiently dissipates energy allowing it to settle into circular orbits, whereas the collisionless stars maintain a velocity ellipsoid that acts as an effective dynamical pressure.  It is this direct link to the galactic potential and the stellar phase-space distribution function that makes asymmetric drift a powerful tool in quantifying the dynamical state of galaxy disks.  I will present two ongoing works.  The first uses data from the DiskMass survey to measure the axial ratios of the stellar velocity ellipsoid, for which asymmetric drift is a key aspect of the measurement.  The second uses data from the recent MaNGA survey in a more general study of asymmetric drift in ~800 galaxies across the color-magnitude diagram.  Finally, I will discuss how our approach and these results could be used to extend the primary scientific goal of the DiskMass survey --- to provide robust, dynamical measurements of the baryonic masses of galaxy disks --- to new regimes.

The cosmic web is the large-scale metric in which galaxies form and evolve. Recent measurements from low-redshift spectroscopic surveys support a picture in which the large-scale environment impacts both the dynamics and the assembly history of galaxies. However extracting the cosmic web from observed datasets is still a challenge, in particular at high redshift where large and complete spectroscopic surveys are extremely costly. At these redshifts, though, we expect a stronger dependency of galaxy properties on the geometry of the accretion, which makes this extraction pivotal to understand galaxy evolution. I will give an overview of the current status of cosmic web analysis from high redshift observations, either photometric data or lyman-alpha forest surveys. While relying on a pilot study in COSMOS, I will present results about the co-evolution of galaxies and the cosmic web at high redshift and I will show how this study can be extended with future probes including LSST, Euclid, PFS and MOSAIC on the ELT.

To understand galaxy evolution it is essential to know how and why the gas content of galaxies evolves. There are several physical processes that can affect a galaxy gas reservoir, and in galaxy clusters ram pressure stripping is considered the most efficient such mechanism. I will show how integral field spectroscopy can be used to study the removal of gas from galaxies in clusters and groups, focusing on the consequences that such removal has for the AGN activity and for the star formation activity in the disks and in the tails of stripped gas.

Integral-field spectroscopic surveys such as MaNGA in the nearby Universe and KMOS3D out to z~2.6 are providing us with a 3D mapping of the ionized gas emission in large samples of mass-selected star-forming galaxies. Their dynamics reveal the depth of gravitational potentials in which the gas orbits. Broad components to the line emission shed light on galactic-scale outflows driven by star formation and active nuclei. Moreover, the spatial distribution of ionized gas emission serves as a tracer of where within galaxies the (unobscured) star formation is taking place. Complementing these rest-optical observations are far-infrared measures of dust and CO line emission, probing the cold gas reservoirs, molecular outflows and the distribution of dust-obscured star formation. I will present recent findings on the nature and evolution of star-forming galaxies from cosmic noon to the present day, obtained by combining multi-wavelength tracers of dust and star formation, ionised and molecular gas.

The strikingly anisotropic large-scale distribution of matter, the so-called cosmic web, is made of an extended network of voids delimited by sheets, themselves segmented by high-density filaments, within which matter flows towards compact nodes where they intersect. Do the properties of galaxies, such as e.g. their morphology, retain a memory of these large-scale cosmic flows from which they emerge? And what are the signatures of this environment at different locations within the cosmic web? In this talk, I will address these questions using the set of observed and virtual galaxies, from the spectroscopic survey GAMA and large-scale hydrodynamical simulation HORIZON-AGN, respectively. I will argue that on top of stellar mass and large-scale density, the traceless component of the tides from the anisotropic large-scale environment also shapes galactic properties. I will show that these results can be qualitatively explained in terms of anisotropic assembly bias by an extension of excursion theory.

The faintest detectable parts of galaxies harbour an impressive amount of information about their evolution and even their formation. But reaching faint surface brightness levels means overcoming a number of severe challenges, including background analysis and light scattering. I will discuss these issues and highlight how we can use ultra-deep imaging to detect faint structures, including tidal arms, ultra-faint dwarf galaxies, and thick disks in edge-on galaxies. I will also discuss how upcoming surveys, including by Euclid and LSST, are bound revolutionise this field soon by allowing us to reach huge samples, as long as we can beat the systematics and handle the resulting streams of 'Big Data’.

Following detection by advance LIGO, gravitational wave (GW) stocks are on the rise. The low frequency GW Universe is likely dominated by signals emitted by a cosmological population of massive black hole binaries (MBHBs). I will review several aspect of MBH astrophysics, including their formation, evolution, interaction with their environment and GW emission. I will then discuss prospect of GW detection with pulsar timing arrays and/or future space based interferometers such as the laser interferometer space antenna (LISA) and for pulsar timing arrays.

A Physicist has so many things to think about at the moment, before they can even get to their research! Public Engagement, Diversity, Widening Participation! They are all so important but can feel like a massive drag. In this talk, I’ll show how they come together and lead to benefits to your Physics. This talk will contain anecdotes and practical examples of projects from my career as a theoretical cosmologist, transport engineer, outreach officer at the IOP, Director of Public Engagement for a partnership of nine physics departments in the South-East and an LGBT+ in STEM campaigner. I’ll also have an update on the latest from the IOP / RAS / RSC’s LGBT+ workplace survey they carried out last year.

Until about a decade ago, star clusters were considered "simple" stellar populations: all stars in a cluster were thought to have similar ages and the same metallicity. Only the individual stellar masses were thought to vary, in essence conforming to a "universal" initial mass function. Over the past decade, this situation has changed dramatically. I will discuss my group's recent progress in this context, with particular emphasis on the properties and the alleged presence of multiple populations in Local Group star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate- age (~1—3 Gyr-old) star clusters, which opens up exciting avenues for future research efforts.

I present results from the recently completed VIPERS redshift survey which has obtained spectra for ~100,000 galaxies at z~0.5-1.2 over 24 square degrees, including >1000 star-forming galaxies with masses above 10^11Msun. I show how the number density of such massive star-forming galaxies has declined five-fold since z~0.8, and how the high-mass limit for the main star-forming sequence has fallen steadily to lower masses over the last 8 billion years. By examining in detail how the D4000 distribution of galaxies at fixed stellar mass has evolved, I show whether secular evolution can explain the observed decline in massive star-forming galaxies or if additional quenching events are required. We show that these massive star-forming galaxies at z~0.8 are the likely progenitors of local S0s.

JWST will revolutionise our understanding of the evolution of high redshift galaxies. Where currently our understanding is limited to discrete samples selected by different mechanisms, with the largest samples derived from selecting galaxies from their rest-frame UV, we will be able to analyse galaxies from mass-selected samples using NIRCam/MIRI. Moreover we will have rest-frame optical spectroscopy using NIRSpec, with Halpha detected up to z~7, which is presently out of reach for current facilities. I will summarise some open questions of high-redshift galaxy evolution that count on future JWST data to disentangle, present the joint NIRCam and NIRSpec GTO survey plans as well as our publicly available mock catalogue designed specifically for survey planning. Finally I will show the results from a case study investigating to what accuracy can we derive physical properties from NIRSpec low-resolution spectra (R~100, covering 0.7-5 microns).

Massive international efforts are currently being deployed to construct predictions tools for upcoming weak lensing analyses, typically aiming at sub-percent precision. Their focuses are primarily set on two-point statistics (e.g. position and/or shape correlation functions), mainly because these can be directly related to the matter power spectrum, which can be accurately obtained from fitting functions and emulators. Weak lensing beyond the two-point statistics can play an important role however, for it has access to more cosmological information given that the matter density field has become non-Gaussian. In this talk I will review recent weak lensing data analysis based on higher order statistics, and discuss requirements for upcoming surveys, with a focus on the calibration with cosmological simulations.

Galaxies and the halos in which they reside are intrinsically connected. That relationship holds information about important processes in galaxy and structure formation, and is key to unlocking the full statistical power of forthcoming redshift surveys and their cosmological analyses. In this seminar, I will consider how the galaxy-halo connection might depend on its position within the cosmic web - the familiar decomposition of large-scale structure in filaments, knots and voids - highlighting recent and ongoing work in observations and in simulations.

The current frontier in cosmology is the charting of the accelerating expansion rate of the universe with time, and thereby characterising the phenomenology of dark energy. Doing so requires ambitious new surveys of galaxies over unprecedented volumes. The Dark Energy Survey is the largest ever galaxy survey and hopes to unlock the potential of gravitational weak lensing, amongst other methods, as a probe for cosmology. In this seminar, I will cover the early constraints that have been achieved on cosmology parameters from science verification data taken with the new DECam. A particular challenge for weak lensing analysis is in understanding the distances to the millions of survey galaxies. I will cover our approach taken during the science verification analysis and the future challenges we face in this aspect of the experiment.

The Epoch of Reionization signals the end of the Dark Ages of the Universe and the birth of the first stars. The race is on to make the first statistical detection of this epoch however the foregrounds swamp the cosmological data by several orders of magnitude and their removal remains a significant challenge for both current and future telescopes. I will speak broadly about the foreground mitigation techniques currently being used with EoR data and take a closer look at the efforts being made by LOFAR with blind foreground removal methods.

Lyman Break Galaxies (LBGs) are the largest population of high-redshift (z > 3) star forming galaxies and as such provide valuable insights into the mass assembly of normal galaxies during the first few Gyr of the Universe. They have moderate star formation rates (~10s-100s Msun/yr) and ~10-100x higher space densities than the more extreme submillimetre galaxy population, thus they should comprise a significant portion of the far-infrared background at high redshift. But determining their true contribution to the far-infrared background has been difficult due to the rather large uncertainties that go hand-in-hand with deriving dust corrected UV luminosities and star formation rates. The only reliable way of measuring the dust content of LBGs is directly through submillimetre observations. In this talk I will present some new results on LBGs selected at z~3, 4, and 5 from a series of different studies using SCUBA-2, Herschel and ALMA.

I will present new results regarding the first ~2 Gyrs of cosmic time using very wide-field Lyman-alpha (Lya) narrow-band surveys, including a large, matched Lya-Halpha survey to investigate how Lya and Lyman-continuum (LyC) photons escape from typical star-forming galaxies at high-redshift. We find that large Lya halos are ubiquitous in star-forming galaxies, and that the typical escape fraction of Lya and LyC photons is typically below a few percent. However, the escape fractions of Lya selected sources are significantly higher. We also find a much higher space density of very luminous Lyman-alpha emitters all the way from z~2 to z~7 than previously assumed, which we confirm spectroscopically with Keck, VLT and WHT. Many of our sources show high-ionisation lines in the rest-frame UV (CIII], CIV, HeII), and some have clear Lya blue wings. At z~7 our sources (e.g. CR7) show signatures of PopIII-like stellar populations (extremely metal poor) and/or direct collapse black holes and provide interesting challenges ahead of the launch of JWST. Our results also show that the steep drop in the Lya luminosity function into the epoch of re-ionisation happens only for the faint Lya emitters, while the bright ones likely ionise their own local bubbles very early on, and thus are visible at the earliest cosmic times.

I will briefly recap the motivation for, and progress towards, numerical modelling of the formation and evolution of the galaxy population - from cosmological initial conditions at early epochs through to the present day. I will focus in particular on the EAGLE simulations. They represent a significant development in this arena, since they broadly reproduce key properties of the evolving galaxy population, and do so using energetically-feasible feedback mechanisms. I shall present a broad range of results derived from EAGLE analyses, concerning the evolution of galaxy masses, their luminosities and colours, and their atomic and molecular gas content. I hope to convey some of the strengths and limitations of the current generation of numerical models.

The far-infrared Herschel Space Observatory has opened our eyes to the cold dusty Universe. Far-IR wavelengths provide arguably the best tracers for star-formation in active galactic nuclei (AGN), since luminous nuclear activity is rather inefficient at keeping dust cold. I will report on studies that bring together the very best modern multi-wavelength survey datasets, from the X-rays to the optical to the far-IR, aimed towards developing a coherent view of the growth of supermassive black holes (in AGN) in relation to the growth of stellar content in galaxies (through star-formation). These studies build on the newest advances in our knowledge of galaxy evolution across most of the Universe's history. I will demonstrate that a positive relationship between star-formation and AGN activity is now clearly seen to z > 2. However, the nature of this relationship supports weak or stochastic co-evolution, driven more by the smooth increase of gas content in normal galaxies over time rather than a dominant role of short, intense episodes, such as star-bursts or mergers. This has important implications for the connections between galaxies and the black holes that reside at their hearts.

Cancelled

Galaxies contains dust, and this complicates our view of the stellar populations in optical and UV light. The position of the Sun close to the galactic plane does not provide a better viewpoint of our own galaxy compared to external galaxies - on the contrary, the situation is even worse. Nonetheless, both the outer and inner view of galaxies are needed. A powerful route to the inner make-up of galaxies is to decode their panchromatic spectral energy distribution, taking into account the direct and dust-reradiated components of stellar light. In this talk I will show recent progress in self-consistently modeling radiative processes in galaxies and in the Milky Way, including the high energy gamma-ray emission, in an attempt to lift the veil on our understanding of the fundamental process of galaxy formation and evolution.

Cosmological simulations predict that massive dark-matter haloes are home to a spectrum of smaller, less massive haloes and gaining access to these low mass haloes gives important clues to the fundamental nature of dark matter. Measurements of the subhaloes are naturally only possible through observations of baryonic tracers. I will discuss two different tracers that will shed some light on the properties of the Local Group’s subhalo population. First, tidal streams are dynamically cold structures that are sensitive to close encounters with dark matter subhaloes. I will discuss recent progress in the modelling of tidal streams, how gaps in streams caused by subhaloes can be efficiently modelled and the current constraints from data. Secondly, many of the larger subhaloes are expected to be the hosts of the dwarf spheroidal (dSph) galaxies in the Local Group. I will discuss progress on non-spherical modelling of dSphs and how flattening can enhance or diminish the expected dark-matter annihilation signals from dSphs. I will close by discussing recent results on the shapes and alignments of the Local Group dSph population.

Over the past ~20 years the high-redshift Universe has been increasingly opened to scrutiny at far-infrared wavelengths, where cool dust emission from star-formation dominates. The dusty star-forming galaxies (DSFGs) and submillimeter galaxies (SMGs), selected at these wavelengths likely represent an important, but short-lived phase in the growth of massive galaxies. These DSFGs often have star-formation rates in excess of ~1000 solar masses per year and are confirmed beyond z~6, although their redshifts and high dust contents make them faint and difficult to study at other wavelengths. Using data from the Herschel Space Observatory I have obtained mid-infrared spectra of SMGs, probing the conditions in their ISM. I will present the results from this spectroscopy program as well as discuss other results from our systemically-selected sample of gravitationally lensed SMGs.

Distant galaxy clusters are powerful laboratories for observing the hierarchical growth of large-scale structure, constraining cosmological parameters, and for studying the formation of galaxies. However, distant (z>1.5) clusters are extremely rare and faint, so locating and studying them poses a significant observational challenge. In this seminar, I will review the theory of cluster formation and present recent advances we have made in detecting and studying distant galaxy clusters.

Universities and funding bodies now tend to agree that public engagement is something to be encouraged. But delivering successful public outreach while holding down a research career isn’t always an easy balance to strike. Marek Kukula, Public Astronomer at the Royal Observatory Greenwich explores some of the ways in which astronomers can engage with a wide variety of audiences including the general public, schools, specialist groups and the media, and looks at how museums and galleries can help to provide a platform for researchers via exhibitions, talks and cross-disciplinary approaches from high art to popular culture. He'll also try to address the question of how public engagement can help early-stage researchers to develop their careers both in outreach and in academia and, time permitting, will reveal how he teamed up with writer Simon Guerrier to explore The Scientific Secrets of Doctor Who. <br><br> <strong>Biography:</strong> Marek completed his PhD in Radio Astronomy at the University of Manchester's Jodrell Bank Observatory and then carried out research into quasars and galaxy evolution at Liverpool John Moores University, the University of Edinburgh and the Space Telescope Science Institute in Baltimore. He subsequently worked for the University of Edinburgh’s Office of Lifelong Learning and as Project Manager for Researchers in Residence, a UK-wide scheme to support early-career academics to work with secondary schools. As the Public Astronomer at the Royal Observatory Greenwich he is part of a team of astronomy education and outreach specialists who engage with the public, schools and the media. The role involves working with scientists, historians and artists to explore the cultural as well as the scientific impact of astronomical research. Marek is a judge on the Insight Astronomy Photographer of the Year competition and has curated several exhibitions, including Visions of the Universe, on the history and impact of astrophotography, at Royal Museums Greenwich in 2013 and dark frame/deep field at the Breese Little gallery in 2015, juxtaposing the work of six contemporary artists with vintage NASA photographs. He is the author of The Intimate Universe and the co-author of The Scientific Secrets of Doctor Who, both published in 2015.

I will give an overview of what we learned in our understanding of galaxy evolution thanks to integral-field spectroscopy.

Active galactic nuclei are among the most powerful astronomical objects in the universe. Though usually located in the core of their host galaxies, their feedback has the potential to influence the dynamics and energetics of their hosts on large scales, even affecting their star formation history. Radio-loud sources, in particular, can efficiently transport energy, through relativistic jets, up to megaparsec scales, influencing cluster gas dynamics and cooling times. I will try to summarise the properties of these objects, why they are important to understand galaxy and cluster evolution, and what surveys and methods we are currently using to study them.

Emission line galaxies trace the cosmic star formation history and moreover, they are being used as tracers of the dark matter distribution up to z~1. We have use a state-of-the-art model of galaxy formation and evolution to study the properties of model emission line galaxies, in particular [OII] emitters. To mimic a range of surveys, we select model [OII] emitters by making cuts in [OII] line flux, optical magnitudes and colours. The model [OII] emitters have luminosity functions in reasonable agreement with observations at z~1. 95% of these model galaxies are centrals hosted by haloes with M halo > 10^11 Msun/h . In the model very few haloes contain more than one [OII] emitter that is a satellite galaxy. Confronting this result to available observations, suggests the need to revise the modelling of hot gas stripping in satellite galaxies. The mean halo occupation distributions of these model galaxies have a global shape typical of star forming galaxies. For central [OII] emitters we have identified that we can split the contribution of central galaxies to the mean halo occupation distribution into an asymmetric Gaussian for central disks and a step function plateauing below one for central spheroids.

The "Lambda cold dark matter" (LCDM) cosmological model is one of the great achievements in Physics of the past thirty years. Theoretical predictions formulated in the 1980s turned out to agree remarkably well with measurements, performed decades later, of the galaxy distribution and the temperature structure of the microwave background radiation. Yet, these successes do not inform us directly about the nature of the dark matter. Indeed, there are competing (and controversial) claims that the dark matter might have already been discovered, either through the annihilation of cold, or the decay of warm, dark matter particles. In astrophysics the identity of the dark matter manifests itself clearly in the properties of dwarf galaxies, such as the satellites of the Milky Way. I will discuss predictions from cosmological simulations assuming cold and warm (in the form of sterile neutrinos) dark matter and show how astronomical observations can conclusively distinguish between the two.

Galaxy clusters are the largest gravitationally bound structures in the Universe, and we know that early type galaxies (ETGs) are more common towards their centres. Clusters of galaxies are increasingly rare at early times, but are essential for understanding the formation of these massive structures and how they alter the fate of their member galaxies. However, long integration times on large telescope are required to constrain the stellar properties of these distant cluster ETGs. Now with the advent of the multiplexed near-infrared integral field instrument, the K-band Multi-Object Spectrograph (KMOS) on the Very Large Telescope, we can target the ETGs in these valuable high-redshift clusters more efficiently than ever. The KMOS guaranteed observing program, the KMOS Cluster Survey (KCS; P.I.s Bender & Davies), has enabled a study of cluster galaxies in overdensities spanning z = 1–2 through absorption-line spectroscopy obtained from 20-hour integrations. I will present KMOS spectra for 16 galaxies and Hubble Space Telescope photometry of the furthest KCS overdensity, JKCS 041, an ETG-rich cluster at z = 1.80. To determine stellar ages of the cluster galaxies, a scaling relation called the fundamental plane (FP) was constructed for seven galaxies in JKCS 041; the highest redshift FP for ETGs in a single cluster. The relative velocities of the galaxies derived from the spectra indicated an infalling group of galaxies, and we determined that these were significantly younger than the rest of the cluster members. Based on the galaxy dynamics, cluster morphology, and galaxy stellar age results, we concluded that JKCS 041 is in formation and consists of two merging groups of galaxies. Our results could link galaxy ages to large-scale structure for the first time at this redshift.

From 2009 to 2014, the Baryon Oscillation Spectroscopic Survey (BOSS) used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known as the Lyman alpha forest (LyaF). In this talk I will overview the final results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the auto-correlation of the LyaF (Bautista et al. 2017), and from its cross-correlation with quasars (du-Mas-des-Bourboux et al. 2017). From the combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty. Starting in 2019, the Dark Energy Spectroscopic Instrument (DESI) will increase this data set by an order of magnitude. DESI will provide an exquisite measurement of the expansion over cosmic time, while at the same time addressing other interesting questions: the sum of the mass of the neutrino species, properties of dark matter particles, tests of general relativity and the shape of the primordial power spectrum of density fluctuations.

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Galactic plane surveys of the Milky Way in a variety of gas or dust tracers give us different perspectives on how the physical conditions of the interstallar medium vary throughout the Galaxy. The Herschel Infrared Galactic Plane Survey (Hi-GAL) covers the peak of the spectral energy distribution of dense, cold dust and thus supplies an essential part of the observational description of the conditions necessary for star formation in the Milky Way. With a catalogue of over 100000 compact Hi-GAL sources, I will discuss how star formation varies as a function of Galactocentric radius and proximity to spiral arms. This allows us to revisit several long-standing questions about the effect large-scale Galactic properties have on star formation on parsec scales. Moreover, with a comprehensive profile of the Milky Way over kiloparsec scales, these results provide a new detailed context in which to understand star formation in external galaxies.

Late last year there was much excitement within the planetary science community, and in the press, about the first macroscopic interstellar object to be discovered passing through our Solar System. I'll tell the story of the discovery of 1I/'Oumuamua, the scramble to observe it before it left, and what we know about it after a couple of months of rapid publication of surprising results.

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Variability in Active Galactic Nuclei has been seen as a defining feature for many years, and has long been seen as problematic for accretion disc theory. However, recent observations of extreme variabiity - factors of many over years - have brought these problems to a crisis. I will summarise the key observations, and examine in turn three possible explanations - microlensing events, tidal disruption events, and accretion disc instabilities.

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Using examples from the XMM Cluster Survey, the Dark Energy Survey, ITV's "Take Me Out", and BBC Three's "Don't Tell the Bride", I will demonstrate the importance of clusters of galaxies to modern Observational Cosmology and some of their down sides. Recent publications to be featured include: The redMaPPer Galaxy Cluster Catalog From DES Science Verification Data; Comparing Dark Energy Survey and HST-CLASH observations of the galaxy cluster RXC J2248.7-4431: implications for stellar mass versus dark matter; The XMM Cluster Survey: The Halo Occupation Number of BOSS galaxies in X-ray clusters; The XMM Cluster Survey: evolution of the velocity dispersion -- temperature relation over half a Hubble time; Crowdsourcing quality control for Dark Energy Survey images; OzDES multifibre spectroscopy for the Dark Energy Survey: first-year operation and results; The XMM Cluster Survey: testing chameleon gravity using the profiles of clusters; Galaxies in X-ray Selected Clusters and Groups in Dark Energy Survey Data I: Stellar Mass Growth of Bright Central Galaxies Since z~1.2. No Likey? No Lightie [where "Lightie" in this context translates to "well, you can always try using weak lensing, but that's a whole other can of worms"]!

A galaxy's visual morphology is primarily determined by its stellar orbits and thus its assembly history. Stars in ordered rotation likely originate from the circular orbits of a gas-disk, while the disordered orbits in bulges reflect more complex formation histories. But while late-type galaxies are easily identified, subtle differences between early-type galaxies (ETGs) are not: a near face-on axisymmetric disk of old stars in a lenticular (S0) looks similar to a genuine ellipsoidal distribution of stars in an elliptical (E). However, integral field spectroscopy can distinguish the kinematics of disks (Fast Rotators, FRs) from ellipsoids (Slow Rotators, SRs): the SAURON & ATLAS3D surveys found that 66% of visually-classified Es contained ordered disk-like rotation and were thus misclassified S0s. With ETGs more common in denser environments, we extend this kinematic classification to the Coma and Abell 1689 galaxy clusters. Although SRs are found in the cluster centres, virtually none are found in the outer regions. Remarkably, the total SR:ETG ratio in each cluster was the same as in the (ATLAS3D) field, just 15%. Revisiting Dressler's original visual galaxy morphologies in 55 clusters we show that a similar result holds: the total E:ETG fraction in each cluster is 30%. Using the statistics from ATLAS3D, we show that these results are equivalent.

The talk will present new expected and unexpected results from the Dark Energy Survey beyond cosmological studies, including solar system objects, Milky Way companions, galaxy evolution, galaxy clusters, high-redshift objects and gravitational wave follow ups (Reference: arXiv:1601.00329).

The Kepler space mission revolutionised exoplanet science by discovering thousands of transiting planets, but the loss of two of its four reaction wheels put an end to the original mission a little over 2 years ago. Luckily, the satellite has been given a new lease of life, in the form of the K2 mission. K2 uses the Kepler satellite to observe 4 fields per year, near the Ecliptic plane, with only slightly reduced photometric precision compared to the original Kepler data, enabling it to survey thousands of particularly interesting targets for planetary transits: bright FGK stars, low mass M-stars, and stars in young open clusters. I am particularly interested in the latter, as it is the first time that we can perform efficient transit surveys in open clusters, and each detected system provides a unique constraint on evolutionary models for low-mass star or planets. In my talk I will give an overview of how we detect, confirm and characterise transiting exoplanets and young binaries with K2. The main challenges include dealing with the systematics effects caused by the reduced pointing accuracy of the satellite, the enhanced variability of young stars, and the challenges of measuring precise radial velocities for planet candidates around active stars. I will give a brief overview of the young eclipsing binaries and candidate planets found by K2 so far, and outline the rich prospects for open cluster science with future missions such as TESS and PLATO.

Understanding the process responsible for transforming star forming galaxies into passive and quiescent systems is currently one of the hottest topics in astronomy. I will discuss recent observational results probing different mechanisms at work in different galaxies and at different epochs. I will present multi-wavelength observations providing evidence that powerful starburst-driven and AGN-driven outflows have a profound impact on the evolution of galaxies, both locally and at high redshift; however such massive outflows may not be able to completely quench star formation in galaxies and actually, in some cases, such outflows can even boost star formation. I will show that the analysis of the stellar metallicities in large samples of local galaxies reveals that “starvation” (or “strangulation”, i.e. the lack of gas inflows) is actually responsible for quenching star formation in most galaxies. I will discuss the possible mechanisms responsible for the starvation of galaxies. I will also present some recent results from the ongoing Manga-SDSSIV survey, which is delivering integral field spectroscopy for thousands of galaxies. Based the analysis of the initial sample of several hundred galaxies I will show evidence that the quenching process in galaxies occurs predominantly inside-out, and I will show that even this observational finding can be explained in terms of “starvation”.

As the faintest galaxies we are able to observe in the Universe, the dwarf spheroidals can be thought of as the fundamental galactic unit. Within our Local Group, we are able to study these objects in extremely high detail, resolving their mass profiles, chemistries, and evolutionary histories. These measurements have led to several surprising results. One is that the masses of these systems appear to be lower than predicted by cold dark matter simulations. Additionally, dwarf galaxies are not distributed isotropically around their hosts, as naively expected in the current cosmological paradigm. In this talk, I will discuss these observational peculiarities, and how we may account for them, using examples of interesting dwarf galaxies in the Andromeda system, and results from recent hydrodynamical simulations.

The exploration of young and metal-poor galaxies across cosmic history is key to deciphering how fundamental processes such as enrichment, feedback, and star formation operated in the first galaxies. However, the spatially-resolved spectroscopic observations that are needed to constrain these physical mechanisms are currently extremely difficult, if not impossible, to perform because the objects are so faint and small. In this talk I will describe several new observing campaigns that resolve this issue by connecting low-metallicity star-forming galaxies in the nearby Universe with distant strongly-lensed galaxies as proxies for the earliest galaxies, including a newly discovered population of young, extremely metal-poor blue diffuse galaxies. I will discuss how the maps of star formation, ionisation, metallicity, and gas kinematics obtained from these observations currently constrain galaxy formation models (including the so-called `bathtub' and `galactic fountain' models), and I will highlight future observational capabilities that will push our understanding of galaxy evolution to even smaller physical scales and earlier times.

I will start with an overview of the state-of-the-art in galaxy formation and large-scale-structure numerical simulations from cosmological initial conditions. On the one hand we wish to simulate large volumes to gain representative samples of galaxies and to understand the cosmological implications of forthcoming survey data from LSST, Euclid and DESI. On the other, we also want to maintain very high resolution to resolve highly non-linear astrophysical processes and internal kinematics for forthcoming galaxy IFU studies like MaNGA. These two requirements result in a tension on how to best spend limited computer time. I will argue that a new approach to simulations, in which we use statistical models to tailor cosmological initial conditions for different questions, can help relieve this tension. I will show a range of applications from large scale power spectrum estimation to galaxy quenching.

Post-starburst galaxies have long been known as an intriguing class of galaxies, identified through their unusual optical spectra as having had a recent burst of star formation that has since quenched. What caused the starburst and what caused the quenching? Originally identified in clusters (so-called E+A or K+A galaxies), they are now known to exist in all environments. They are rare at low-redshift, but increasingly common at high redshift. I will review recent progress in studying post-starburst galaxy properties, focussing on the question of whether they are true “transition” species i.e. galaxies transiting from the blue cloud to the red sequence, and how important they could be for accounting for the growth of the red sequence since z~2.

Gravitational lensing has seen a surge of interest in the past few years. Lensing is one of the very few probes capable of mapping dark matter halo distributions. Lensing also provides independent cosmological parameter estimates and enables the study of galaxy populations that are otherwise too faint for detailed study. The handful of strong lensing systems known in the year 2000 has now been replaced with hundreds, thanks to innovative multi-wavelength selection, and there is an imminent prospect of thousands of lenses from Herschel and other sub-millimetre surveys. I will show how Euclid and the Square Kilometre Array promise tens or even hundreds of thousands of strong lensing systems, and some early results from our long-term project on the 10m Southern African Large Telescope, which is extremely well placed to have an enormous impact in follow-up observations of foreground lenses and background sources.

Active Galactic Nuclei (AGNs) are amongst the most powerful individual objects in the Universe. Powered by material accreting onto supermassive black holes at the centres of galaxies, the energy released by AGNs is widely thought to have played a major role in shaping today's galaxies. Despite their importance, fundamental questions still surround many aspects of AGNs, not least what governs their accretion rate (and thus power output) and how - or indeed whether - they influence their host galaxies. In this talk, I will summarise the exciting progress that has been made in both these areas of AGN astronomy over the past decade, while highlighting what key questions still remain to be addressed.

It is now clear that the conversion of interstellar gas to stars, along with the subsequent feedback from massive star formation are fundamental agents in the shaping, evolution, and formation of galaxies. Thanks to a wealth of new multi-wavelength observations from the ground and space our empirical understanding of these processes is being revolutionised, yet our understanding of the underlying physical processes which trigger and regulate large-scale star formation remains embryonic. This talk will review what we have learned in the past decade about the demographics and diversity of star formation in galaxies, its evolution over cosmic time, and the empirical correlations and scaling laws that offer clues to deeper underlying physical processes of star formation and galaxy evolution.

One of the best ways of studying compact objects in the Universe, such as white dwarfs, neutron stars, stellar-mass black holes, exoplanets and Solar System objects, is through their brightness variations. These tend to occur on timescales of seconds and below, and hence require specialised astronomical instrumentation. In this talk, I shall review the design and scientific highlights of the high-speed cameras ULTRACAM, ULTRASPEC and HiPERCAM, the first two of which have been in operation for over a decade, and the last of which is due to see first light next year on the largest optical telescope in the world.

In a hierarchical Universe clusters grow via the accretion of galaxies from the field, groups and even other clusters. As this happens, galaxies lose their gas reservoirs via different mechanisms, eventually quenching their star-formation. One of the most effective mechanisms in clusters is ram-pressure stripping by the intra-cluster medium. I will present recent results from multi-wavelength observations of z<0.2 clusters that are helping to constrain the efficiency, time-scale, and consequences of stripping. In particular, I will present a phase-space analysis of HI-stripping and star formation in cluster galaxies, and show recent MUSE/VLT observations of the most extreme examples of stripping, the so-called "jellyfish galaxies".

Observing galaxies in the Far-Infrared (FIR) gives us a unique window into the star formation rates of very high redshift, dusty galaxies. These galaxies are generally thought to be forming stars at a prodigious rate, heating their dust content, which then radiates in the FIR. However, observing this glow is difficult, even with a space-based telescope such as the Herschel Space Observatory, as the resolution of the images returned is quite poor. It is often assumed that a bright source in the FIR belongs to a single, highly star forming galaxy, but this is impossible to verify with low resolution images. In this talk I will discuss a new method of unpicking a single FIR detection into individual galaxies, and what the results of this unpicking imply for our understanding of galaxies in the early Universe.

I will present a selection of results and ongoing projects in radio weak lensing. I will present forecasts which suggest that the SKA will be capable of world-leading weak lensing cosmology, potentially providing additional information to help remedy a number of systematics which could limit optical and near-IR weak lensing. In addition, cross-correlating cosmic shear measurements between optical and radio bands gives comparable constraints and should be free of many wavelength-dependent systematics. In order to achieve this promise, many challenges need to be solved and I will discuss a few of them. Outstanding questions include how to measure shapes from radio interferometer data, how to model the source galaxy population at faint micro-Jy fluxes, and how to estimate their redshifts. I’ll also discuss a number of radio weak lensing pathfinder surveys on which we are developing and training the required new analysis techniques.

Recent observations have shown that the properties of the dense intracluster gas cooling in the cores of clusters of galaxies are significantly affected by AGN activity in the central brightest galaxy. I will review these observations and focus on the most nearby example of this AGN Feedback from NGC1275 at the core of the Perseus cluster.

In this talk I will describe how mapping the dynamics of molecular clouds in the centre of galaxies can help us to constrain a wide range of astrophysical problems. From the enigmatic relation between galaxies and their supermassive black holes, the suppression of star-formation in dying galaxies, and the puzzling variation of the stellar initial mass function, molecules provide an ideal probe that can help us make progress. I will show how high resolution observations (with CARMA and ALMA) can be used to estimate the masses of supermassive black holes in galaxies across the Hubble sequence, and describe the WISDOM project, that aims to use this technique to constrain the importance of accreting SMBHs in galaxy quenching. I will show that the deep potential wells of massive galaxies can play an important role in quenching star-formation, transitioning galaxies as they grow from star-forming to "red and dead". Finally I will show how one can use molecules to probe the controversial topic of variation in the stellar initial mass function.

Studying galaxies at high redshift (z > 6) provides a unique insight into the early stages of galaxy formation and evolution. The samples of star-forming galaxies discovered during this epoch have largely come from deep HST surveys, with wider-area ground-based data providing key constraints at the bright end. I will present our results from two degree scale near-infrared surveys (UltraVISTA/COSMOS and UDS/SXDS), looking at the bright-end of the luminosity function at z = 6 and 7. Studying the galaxies in more detail with Spitzer and HST, we find evidence for strong rest-frame optical emission lines such as [OIII] and a clumpy/merger-like morphology for the brightest objects. I will end with a discussion of our new analysis of the strong Lyman-alpha emitter, and potential Pop III candidate, CR7.

The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST). Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals. The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s. I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan.

In recent years there has been tremendous progress in identifying large samples of distant galaxies, but many crucial aspects of galaxy formation remain poorly understood. In particular, we still do not understand why star formation was abruptly quenched in many massive systems at high redshift. It is also unclear if the same processes are linked to the morphological transformation of galaxies, to produce the Hubble Sequence we see today. I will discuss recent observational and theoretical progress in this area, and present new evidence suggesting that the key transformative processes are intimately linked; for the most massive galaxies at least, the quenching of star formation appears to occur during (or very shortly after) the event that forms the compact proto-spheroid.

Mapping Nearby Galaxies at Apache Point Observatory (MaNGA, part of the fourth incarnation of the Sloan Digital Sky Surveys or SDSS-IV), is partway through it's ~6 year programme to obtain spatially resolved spectral maps for ~10,000 nearby galaxies selected from the SDSS Main Galaxy Sample. These data will unwrap the layers of local galaxies - revealing their stellar and gas dynamics, as well as the ages and chemical make-up of their constituent stars, and locations of current star formation. MaNGA began observations on the Sloan Telescope at APO in July 2014 and is now the largest sample of resolved spectroscopy in the world, with ~3300 galaxies observed to date. MaNGA will provide an amazing census of the stellar and ionized gas content of galaxies for a representative sample of nearby galaxies. However, complementary information about the cold gas content is crucial for a number of applications, but especially understanding the physical mechanisms that regulate gas accretions and quench galaxy growth. In this seminar I will describe the HI-MaNGA project which is one of the follow-up projects for MaNGA focused on learning about cold gas components. For HI-MaNGA we have been awarded almost 1000 hours of time on the Robert C. Byrd Green Bank Telescope (in West Virginia) to obtain 21cm HI (neutral hydrogen) global profiles of ~600 MaNGA galaxies. I will explain how measuring the total HI content of MaNGA galaxies can add to our understanding of the physical mechanisms regulating star formation in galaxies, as well as show some interesting early results from the project.

The first detections of gravitational waves from binary black hole mergers have opened up new opportunities and challenges in astrophysics and fundamental physics. I will describe these recent discoveries and discuss advances in the analysis and interpretation of gravitational-wave observations. I will focus on my group's efforts to extract the astrophysical evolution of massive stellar binaries from observations of gravitational waves emitted during mergers of the stellar remnants.

Galaxy clusters are the most massive structures in the universe and their mass growth provides a unique test for cosmological models of structure formation. Clusters are also the location where many galaxies have their star formation strongly truncated, and this process is still poorly understood. I will present new results on the growth of stellar mass in clusters over ~10 Gyr of cosmic time which shows they are highly concentrated at early times and are growing in an inside-out manner, something that is not seen in most simulations. I will also present new constraints on the timescale and location for quenching of galaxies in the cluster environment at early times. These timescales are showing us that the process by which clusters quench star formation is likely evolving over cosmic time, and that we clearly need to invoke much more sophisticated models of environmental quenching and feedback in galaxies if we are to truly understand how galaxies evolve in high-density environments.

Observations of molecular gas in distant galaxies are experiencing a coming-of-age, transitioning from a "discovery" to a "survey" mode. New and upgraded facilities are now making it possible to survey molecular gas efficiently in large galaxy samples, and these observations are proving to be critical in refining our general picture of galaxy evolution. In this talk, I will review recent results from the two largest surveys for molecular gas in normal star-forming galaxies, the z=0 IRAM-30m COLD GASS survey and the z=1-2 IRAM-PdBI PHIBSS survey, and show how they combine to lend strong support in favor of the "equilibrium" model for galaxy evolution, under which most of galaxy evolution is regulated by gas supply and the efficiency of the star formation process.

Stellar halos contain information about various stages of galaxy formation, from the incipient stages of in situ star formation to the later episodes of accretion and tidal disruption of dwarf galaxies. Recent gas-dynamical simulations suggest that the inner halo may be formed from the destruction of a previous galactic disc by merging with satellite galaxies or, less violently, by quasi-secular rearrangement of a proto-disc. The various mechanisms of halo formation leave different signatures in the present-day mass distribution of halo stars or in the spatial distribution of their chemical abundances. I will review the global properties of stellar halos from several recent gas-dynamical simulations and discuss the level of agreement among these and with the available observational data.

We illuminate the thermal and ionization history of the intergalactic medium (IGM) by confronting cosmological hydrodynamical simulations of the IGM with the latest observational constraints on the IGM temperature, the statistics of Lyman-alpha emitters and the opacity of the Lyman-alpha forest, as well as with the latest Planck measurements of the Thomson scattering optical depth towards the CMB.

In this talk, I will discuss the result of a study of extremely isolated galaxies residing in voids in the Galaxy and Mass Assembly (GAMA) survey. While the majority of these galaxies are blue, star forming objects with (u-r) < 1.9, we identify a number of void galaxies with optical colours consistent with no ongoing star formation. A line strength analysis reveals these galaxies to have nuclear spectra consistent with old stellar populations. However, when the mid-IR colours of these galaxies are examined, we find that only void galaxies with masses > 10^10 Msun have truly passive stellar populations. Given their isolation, these highest mass void galaxies have likely undergone mass quenching.

Galaxy luminosity functions are used to measure the distribution of galaxy masses and star formation rates, and are thus critical for measuring galaxy growth and for constraining galaxy formation models. Though functions have been measured in many wavelengths, very little research has focused on what actually shapes the galaxy luminosity function, and as a result, many functions are fitted empirically rather than with physically motivated functional forms. To address this issue, we have measured luminosity functions which trace galaxy stellar mass, as well as functions which trace current star formation, as functions of galaxy morphology and of galaxy optical colour. As dark matter halo mass and stellar mass have a strong correlation, we show that functions of the two share a similar form. Star formation does not have such a clear correlation, and we propose a new method for fitting star forming luminosity functions by convolving models of the star formation rate duty cycle with functions of stellar mass.

Mergers of compact binaries involving neutron stars lie at the intersection of several key problems in astrophysics. They are widely thought to lead to short-duration gamma-ray bursts; to be an important production site for the nucleosynthesis of r-process heavy elements; and to emit strong gravitational wave (GW) signals that are the most promising for detection by the next "advanced" generation of detectors. Recently, the first evidence for kilonova emission, predicted to be produced by the radioactive decay of species created during such a merger, was found, associated with sGRB 130603B. I will review this discovery together with other observational constraints on the nature of sGRBs, and consider the prospects for kilonovae as electromagnetic signatures of GW events.

Biomedicine and astronomy face similar challenges in dealing with increasingly large and complex data-sets which can include multi-modal, multi-spectral and multi-dimensional measurements. This presentation will address potential synergistic overlap of biomedical and astronomical signal processing approaches. I will particularly focus on magnetic resonance imaging (MRI) and magnetoencephalography (MEG), which are the techniques that underpin the research carried out at the Sir Peter Mansfield Imaging Centre, touching on data processing methods used in functional MRI, quantitative susceptibility mapping and measurement of resting state brain networks.

The last few years have seen an explosion in our knowledge of extra-solar planetary systems. We now know that exoplanets have an extraordinary range of properties, and almost every conceivable planetary architecture seems to exist in nature. Planets form in cold discs of dust and gas around young, newly-formed stars, and in this talk I will try to explain how such a diverse population of planets formed from these relatively homogenous initial conditions. I will first review the physics of protoplanetary disc evolution, and discuss the conditions under which planets form and migrate. I will show how disc evolution and dispersal influences migrating planets, leading to "deserts" and "pile-ups" in the distribution of exoplanets. I will then consider the new class of compact planetary systems discovered by Kepler, and discuss under what conditions it is possible to build these systems through migration. Finally I will present models of disc evolution in binary systems, and consider the fo rmation and dynamics of circumbinary planets such as Kepler-16b.

The Hubble Frontier Fields (HFF) initiative constitutes the largest commitment ever of HST time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. This program devotes 140 orbits of HST time to deep imaging observations of each of six cluster lenses reaching m~29 (AB) uniformly in all pass-bands (10-30 orbits per filter - 3 ACS and 4 WFC3 pass-bands). The full set of data on Abell 2744 (z=0.308) has been taken in October-November 2013 with WFC3, and May-July 2014 with ACS. The second target, MACSJ0416.1-2403 (z=0.397) has been observed with ACS in January-February 2014, and with WFC3 in July-August 2014. I will present the new gravitational lensing pictures of these two complex systems using this exquisite set of data coming from the HFF program. We have demonstrated that we are now able to 'weight' these clusters' cores down to the percent level precision (recently published works), serving our quest for the high-redshift Universe.However, while the depth of these dataset makes these clusters amazing Cosmic Telescopes, it also enables us to get an unprecedented understanding of the cluster physics. Therefore, presenting the case of MACSJ0416 & Abell 2744, I will demonstrate the importance of such high-quality data to analyse the merging/dynamical history of the clusters themselves while comparing dark matter, light and gas distributions.

I will discuss observations of environmental quenching using spectroscopic redshift surveys from the local universe to redshift ~ 1.5. Ultimately, I will use these observations, together with numerical simulations, to infer how long it takes satellite galaxies to quench at a range of redshifts. This evolution of satellite quenching times gives important insights into the physical mechanism driving this quenching and into the general baryon cycle of galaxies.

The WISE all-sky survey has discovered some of the most luminous dusty galaxies in the sky. Very powerful AGN, they appear to be surrounded by an excess of other powerful dusty galaxies that are similar to the submillimetre-selected galaxies SMGs. I will describe some of the features of the WISE-detected objects, and the potential for investigating them using ALMA and probing their role in reacting to and shaping their environments.

I will outline our past views regarding what it takes to find the mass of molecular hydrogen gas in galaxies, and what maintains the thermal and kinematic state of this, most important fuel for star-formation in the Universe. Then I will discuss how these views are now being dramatically revised, especially for vigorously star-forming galaxies, and outline the new paths of Interstellar Medium (ISM) research that have opened up as a result. ISM novices are especially welcome, for now is the time to start anew....

I will discuss the evolution of morphological and star-formation properties of galaxies focusing on two aspects: (1) the effect of environment on local group galaxies and (2) the frequency of major mergers vs. disk instabilities in high-z galaxies.

How the first generations of galaxies build up and how they bring the reionisation of the neutral gas in the intergalactic medium during the first Gyr of cosmic time remains one of the biggest questions in extragalactic Astronomy. While the launch of the James Webb Space Telescope will soon provide us with many new insights into this early epoch, we can already learn a lot about the properties of the earliest galaxies with use of current facilities. I will discuss how we can use extremely deep Hubble and Spitzer photometry in combination with rest-frame UV spectroscopy to further our understanding of early galaxy formation processes and the sources of ionising photons in the reionisation era.

In traditional models of galaxy evolution, feedback associated with an active galactic nucleus (AGN) have been invoked as the standard channel to regulate stellar mass growth at the high end of the mass function. We have been investigating a sample of massive, compact galaxies that exhibit ultra-fast gas outflows (up to 2500 km/s) with no evidence of significant AGN activity. Recently we have shown that in at least one of these galaxies a significant amount of molecular gas is being driven out at speeds of up to 1000 km/s to scales of 10 kpc (Geach et al., 2014, Nature). I will discuss how this sample demonstrates that stellar feedback can be an effective channel for curtailing stellar mass growth in massive galaxies, and in particular the role of stellar radiation pressure as a mechanism for launching galaxy scale multi-phase super winds from high density star forming regions.

I will provide an overview of the current understanding of cosmology and galaxy evolution from radio continuum surveys, and show how this field will be revolutionised over the coming years, on the lead up to the SKA.

The nucleosynthesis of the lightest elements of the periodic table, hydrogen, helium, lithium and their isotopes, during the first few minutes of our Universe history is one of the cornerstones of the standard model of cosmology and particle physics. In the last few years, it has become possible to determine the primordial abundances of these elements with high precision, finally realising their long-appreciated potential for measuring the cosmic density of ordinary matter. In this seminar, I shall review the latest developments in the determination of the primordial abundance of deuterium in particular, using the technique of QSO Absorption Line Spectroscopy. The 'punch line' is that independent measures of the density of baryons at different cosmic epochs are in excellent mutual agreement. Such concordance places interesting limits on the existence of relativistic particles beyond the standard model of physics.

In this talk I will discuss which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morphologies in the present day Universe and argue that the black hole feedback is necessary for the quenching of massive galaxies. I will then demonstrate how black hole - host galaxy scaling relations depend on galaxy morphology and colour, highlighting the implications for the co-evolutionary picture between galaxies and their central black holes. In the second part of the talk I will present a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves. I will demonstrate that with this new numerical technique it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations, allowing to track reliably gas angular momentum transport from Mpc to pc scales. Finally, I will also discuss if AGN-driven outflows are more likely to be energy- or momentum-driven and what implications this has for the redshift evolution of black hole - host galaxy scaling relations.

The INT Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS) started in 2004 and is now complete apart from some updates to even out the data quality. The companion blue survey, UVEX, started a couple of years later and at the end of 2011 coverage of the Southern Plane, via VPHAS+ running on the VST, got underway. Between them, these surveys provide imaging in u,g,r,i and H-alpha of the complete Galactic Plane within the latitude range |b| < 5 degrees, down to at least 20th magnitude. In this talk, I will give some of the background on these surveys before focusing on a number of results from them that relate to the large scale properties of the plane of the Milky Way. These will include extinction mapping of the northern Plane and a comprehensive search for massive stars in the south.

Diverse astrophysical and cosmological observations indicate that most of the matter in the Universe is cold, dark and non-baryonic. Weakly Interactive Massive Particles (WIMPs) are generically a good dark matter candidate and particle physics provides us with a well-motivated WIMP candidate in the form of the lightest supersymmetric particle. WIMPs can be detected indirectly (via the products of their annihilation) or directly (via elastic scattering in underground detectors). After an introduction to WIMPs and their detection I will focus on direct detection experiments, in particular astrophysical uncertainties and how they can be addressed.

On the largest of scales, the Universe is organised in to a so-called "cosmic web" - with galaxies being funnelled along filaments that surround voids and in to the nodes of the web -- clusters of galaxies. As they do so, they evolve and change. The question of how galaxies form and evolve over time within the cosmic web is one that has been with us for many years now and research in this area has only accelerated and thrown up more issues as problems get solved and raise new ones. In this talk, I will outline my recent contributions to this field by examining how galaxies in the local Universe are evolving (or not) and how biases in certain datasets can affect the degree of confidence we have in galaxy evolution. I will show new results on the HI content of galaxies in the cosmic web taken from a unique marriage of the 6dFGS survey and HIPASS radio data and highlight our recent work on the Coma cluster that suggests a number of studies may be biased when using this cluster as a redshift=0 baseline to compare other higher redshift clusters to.

I will review what we know about the accretion flow in the stellar mass black hole binary systems, and show how we can use them to test Einstein's General Relativity in strong gravity. The resulting accretion flow models and their associated jet can be scaled up to the supermassive black holes to give some physical insight into the zoo of different types of AGN and Quasars.

The discovery that supermassive black holes reside in the centers of most if not all massive galaxies has emphasized the importance of Active Galactic Nuclei (AGN) in galaxy evolution. Despite this, the processes that trigger Active Galactic Nuclei remain poorly understood. While low luminosity AGN require fuel supplies low enough to allow fueling through so-called secular processes, the gas masses required to power luminous AGN are so large that major mergers of gas-rich galaxies are likely the only triggering mechanisms. However, the observational evidence for a connection between mergers and AGN remains weak. I will present a HST CANDELS study analyzing AGN host galaxy morphologies in a sample of moderate redshift (z=0.5-0.8) AGN spanning a wide range of luminosities. I will discuss if and how the importance of mergers changes as a function of AGN luminosity.

The history of disk galaxy simulation is dotted with remarkable successes, tempered by frustrating impasses, including an inability to recover anything remotely similar to the Milky Way. Recent advances suggest that we might have made a breakthrough by generating essentially bulgeless disks. I will examine the evidence for this new-found optimism and identify where the shortcomings suggest we should be concentrating our future efforts.

Some of the most extreme star formation in the Universe occurs in a population of dusty galaxies at z~2, selected at submillimeter wavelengths (SMGs). Resolved studies of the star forming gas and the fuel for the star formation in SMGs have provided extensive information about the origin of their properties and imply that these systems may be the progenitors of the massive galaxies in the local Universe. I will present observations of SMGs from Integral Field Units, used to study the ionised gas morphologies and dynamics, testing if they consist of merging components. I will then present the results from observing SMGs using millimeter interferometry to probe the molecular gas and the cold neutral interstellar medium, constraining the physical conditions within the SMGs. I will discuss the implications of these results on models of the evolution of massive galaxies. I will then explore the next stage of this evolution, from a merger induced starburst (the SMG phase) to a UV luminous quasar, by discussing observations of reddened quasars which may represent this transition phase.

We present FIR−CO luminosity relations (i.e., log LFIR = a log L′CO + b) for the full CO rotational ladder continuously from J = 1 − 0 up to J = 13 − 12 for a sample of 76 (Ultra) Luminous Infra- red Galaxies (LIR > 1E11Lsun) using date from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1), by including 49 (sub)-millimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well- sampled FIR/sub-millimeter spectral energy distributions (SEDs) so that accurate FIR luminosities can be deduced. The luminous starbursts at high redshifts enlarge the range of the FIR−CO luminosity relations towards the high IR-luminosity end while adding more mid-J/high-J CO line data (J=5–4 and higher) that have been scarce until the advent of Herschel. The now much enlarged dataset (both in terms of IR luminosity and J-ladder) reveals linear FIR−CO luminosity relations (i.e., a ≃ 1) for J = 1 − 0 up to J = 5 − 4, with a nearly constant normalization (b∼2-2.5). This is expected from the also linear IR-(molecular line) relations recently found for the dense gas tracer lines, as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J = 6 − 5 and up to the J = 13 − 12 transition we find increasingly sub-linear slopes and higher normalization constants the higher the J-ladder. We argue that these are caused by a new warm (∼100K) and dense (> 104 cm−3) gas component whose thermal state is not maintained by the SF-powered far-UV radiation fields (and thus is no longer tied to the SFR) and one that is increasingly present towards the high LIR end. The IR-normalized global CO SLEDs that remain mostly flat from J = 6 − 5 up to J = 13 − 12, and are a generic feature of the (U)LIRGs in our sample, further support the presence of such a gas component.

It is well known that stars observed in the local universe form with something very close to a universal initial mass function (IMF) where the vast majority are of low mass. However, this cannot be the case for the very first stars to ever form as a similar IMF would yield many surviving to the present day, contradicting the fact that none have ever been observed. Theory and simulation have also suggested that the first stars likely had a more top-heavy IMF owing to their unique chemical makeup. This implies that a transition in star formation modes must have taken place at some point in the history of the universe. Like the formation of the first stars, this critical epoch exists outside of the range of direct observation and, as such, has been primarily the domain of theory. I will give a review of research into the formation of the first (Population III) stars and theories of the transition from Population III to modern-day star formation. I will then present new results from a set of simulations designed to directly simulate the conditions of this period. Finally, I will conclude with a discussion of the yt simulation analysis toolkit, whose aim is to become a lingua franca for astrophysical simulations by allowing researchers to focus on physical objects instead of files on disk, regardless of the simulation code they use.

In principle galaxy clusters offer powerful constraints on the dark energy equation of state, and opportunities to test gravity theory. These exciting goals can only be achieved at a useful level of precision if the mass of galaxy clusters can be measured accurately. One of the main aims of the Local Cluster Substructure Survey is to calibrate clusters as cosmological probes as part of the global effort to characterise dark energy. I will present new results on cluster mass measurement from our programme of lensing, X-ray, and infrared observations of clusters at z=0.2, and discuss their implications for cluster cosmology. I'll also mention our work on galaxy evolution in clusters if time allows.

Relativistic jets from active galactic nuclei are now known to play an important role in galaxy evolution in the nearby Universe, with their role at higher redshifts remaining uncertain. In the near future, deep extragalactic surveys with next-generation radio telescopes will lead to an unprecedented view of the low-luminosity radio jet population to high redshifts. Translating radio-galaxy population statistics into a robust understanding of the evolving role of radio jet feedback in galaxy evolution requires solving decades-old uncertainties in the physics, energetics and environments of radio-loud AGN. I will discuss recent advances in this subject, driven by the powerful combination of X-ray and radio observations, including early results from the Low-Frequency Array (LOFAR).

The current wisdom is that stars form in molecular clouds as a consequence of turbulent fragmentation. I will discuss what constraints are placed on this theory by observation and what successes the theory has had in satisfying the constraints, the roles played by thermodynamics and feedback in regulating star formation, and the many problems that remain to be solved. I will illustrate, with SPH simulations, some of the processes that may be at work.

Studies of weak gravitational lensing on a cosmic scale are beginning to provide interesting results which are adding to our knowledge of cosmology, and there is promise of precise measurements of the properties of dark energy and modified gravity with future surveys. In this talk, I will show recent results related to CMB lensing and galaxy lensing, showing on the one hand beautiful agreement with theory, and on the other, an indication that things may be more complicated than we think.

In recent years, the concept of the Virtual or Digital Earth has gained currency and a new international society has been set up to develop it further. However, attention has focussed on the surface of the planet and it could be argued that the virtual Earth is hollow. Geologists are working through international initiatives such as the Group on Earth Observations to add the third dimension. The techniques used and the observations made are increasingly available for other planetary bodies, such as Mars, for which we have even less subsurface information. By developing methods to populate the Earth’s third dimension, we also develop ways to do this on Mars. The talk will set out some of this context and then describe ongoing and planned work in NGI and partner organisations that aims to address these challenges.

One of the most important, but still highly debated, issues in contemporary cosmology, is the formation and evolution of massive spheroidal galaxies. Extensive semi-analytic galaxy formation models (SAMs), still debate whether mergers have played a major role in the assembly of ellipticals, or other "in-situ" processes, such as strong, dissipative early bursts of star formation, and/or clumpy accretion, have played an equally important role. In this talk, I will discuss the global evolution of massive spheroids, adopting state-of-the-art SAMs, as well as advanced semi-empirical models. In particular, I will show that, at variance with several previous attempts, hierarchical models can faithfully reproduce the overall shape, normalization, and scatter of the local size-stellar mass relation for massive early-type galaxies as measured in SDSS. I will then move on discussing the role of progenitor bias and environment in the overall structural evolution of massive galaxies. I will conclude with the additional constraints obtainable from lensing measurements on the global profile of galaxies.

I will present results from bulge-disk decompositions of massive galaxies at \(1 \lt z \lt 3 \) in the CANDELS survey and discuss the implications of our findings within the context of some of the current models of galaxy evolution and quenching. By decomposing the galaxies in our sample according to their H(F160W)-band light fractions and extending this analysis across multiple bands, we have been able to conduct SED fitting of the separate components. In addition to morphological properties, this has provided us with individual component stellar-mass and star-formation rate estimates. These decompositions have allowed us to explore the evolution of the galaxies in our sample split into their bulge and disk, star-forming and passive sub-samples, and has provided new insight into the links between quenching and morphological transformations within these systems.

Using new data from the Keck telescope I report on the scaling relations of small stellar systems, ie globular clusters, ultra compact dwarfs, dwarf and compact ellipticals. The elevated mass-to-light ratios seen in some of these systems may indicate either the presence of dark matter, central black holes or a bottom-heavy IMF. Various scaling relations are investigated to shed light on which of these interpretations is most likely. The origin of cEs and UCDs is also discussed.

One of the most important questions in astronomy today is the source of the ionising photons that caused a predominantly neutral Early Universe to evolve into the ionised one we see today. I have investigated this Epoch of Reionisation with a a new suite of high resolution hydrodynamical simulations, created within the DRAGONS group. These simulations show that the galaxies observed at early times represent merely the tip of an iceberg; with a hidden population of faint galaxies that can Reionise the Universe with ease. Although the global star formation history of the early universe is strongly constrained by current observations, we actually know little about the nature of star formation at this time (as given by the specific star formation rate). I will demonstrate that we can understand these objects but need to push our observations deeper, a goal that will likely have to await the James Webb Space Telescope.

The most massive galaxies (M_stellar > 10^11 M_sun) are still very mysterious objects because they display extremely small sizes (~1 kpc) at z > 1.5 and therefore a remarkable change in their observational properties is necessary to match them with their local Universe counterparts. In particular, their size-mass relation has been subject to a great debate because high redshift observations may lose the light from the extended low surface brightness galaxy outer parts. Thanks to the depth, resolution and careful data reduction of the Hubble Ultra Deep Field 2012 programme we are able to detect extended stellar haloes for the six massive Early-Type Galaxies (ETGs) located in this image at \(z \lt 1\). We are able to measure reliably their surface brightness profiles out to ∼31 mag arcsec^−2 , which translates into >25 effective radii or >100 kpc for some objects in our sample, making our observations comparable to the nearby Universe studies but at much larger cosmic distances. Once the faint component is included in our analyses, it has only a reduced impact in the structural parameter estimations, reinforcing the reported compactness of the massive galaxy population at high-z. The presence of these extended stellar haloes, along with dim tidal features and a large number of galaxy satellites seem to be common for massive galaxies. HUDF images are not only useful for investigating the highest redshift galaxies but they also open up a window for the comprehension of the local Universe.

Bayesian inference provides a self-consistent method of model comparison, provided that i) there are at least two models under consideration and ii) all the models in question have fully-specified and proper parameter priors. Unfortunately, these requirements are not always satisfied in astronomy and cosmology: despite the existence of exquisitely-characterised measurements and quantitative physical models (i.e., sufficient to compute a believable likelihood), these models generally have parameters without well-motivated priors, making completely rigorous model comparison a formal impossibility. Still, huge advances have been made in cosmology, in particular, in the last few decades, implying that model comparison (and testing) is possible in practice even without fully specified priors. I will discuss the above principles and then illustrate some test cases of varying rigour, outlining some schemes for formalising heuristic approaches to model testing within a Bayesian framework.

I'll be presenting a study of galaxies in the Herschel-ATLAS local volume \(z \lt 0.05\). We have found that most of the galaxies in the local volume are low surface brightness, blue and dust rich, with very cold dust temperatures. The average gas fraction of the dust selected sample is 0.5, which is very much higher than the average gas fraction of typical optically selected samples. I'll describe the properties of these sources and ask how representative they may be of galaxies in the early Universe.

The Diffuse Gamma-Ray Background (DGRB) is the radiation that remains after the contribution of Galactic gamma-ray emission and extragalactic sources is subtracted from the total gamma-ray flux. The DGRB collects the radiation of all those sources that are too faint to be resolved individually and, thus, it represents an essential tool to study faint gamma-ray emitters like star-forming or radio galaxies and the exotic Dark Matter. I will review our current knowledge of the nature of the DGRB, presenting the strategies that have been proposed to study it. I will focus, in particular, to what we can learn from the measurement of its angular anisotropies.

The polarization of the Cosmic Microwave Background (CMB) has had significant attention this year in light of results from the BICEP2 experiment. I will review CMB polarization and describe how it can be used to test cosmic inflation via gravitational wave signatures. It can also be used to probe other features of the primordial universe, and to trace the cosmic web of dark matter via its gravitational lensing signal. I will describe the ACTPol experiment, currently in operation in Chile. It measures the CMB polarization at high resolution and overlaps with several optical large-scale structure surveys. I will show first results from data measured in 2013, and discuss prospects for cosmology. I will also describe preparations for the next stage Advanced ACTPol project, which will map the CMB polarization over half the sky at multiple wavelengths.

Powerful radio jets launched by a central supermassive black hole pump a substantial amount of energy into their surrounding galaxies and cluster environment. This active galactic nucleus feedback is now thought to be the essential mechanism in galaxy formation models regulating galaxy growth by suppressing gas cooling and star formation. But many key questions remain, including how the black hole is fuelled, how the heating can be distributed over large scales yet closely coupled to the gas cooling rate and the role of the cold molecular gas apparently cooling from cluster atmospheres. I will present ALMA Early Science observations of molecular gas in the central galaxies of A1664 and A1835 which show spectacular 10 billion solar mass outflows driven out by the radio jets and a massive gas inflow settling into a disk around the nucleus.

Black holes in our Galaxy, such as those in the microquasars SS433 and Cygnus X-3, demonstrate dynamic behaviour in accretion and dramatic mass outflows. We observe winds and relativistic plasma jets to emerge from these objects which resemble the modes of mass-loss in the supermassive black holes of powerful quasars in the distant universe. Time-resolved observations of the accretion and subsequent mass-loss from microquasars offers great rewards in terms of information about the nature of these remarkable phenomena in the Universe. I will describe how combined multi-wavelength strategies across the electromagnetic spectrum continue to yield new discoveries and discuss how time-resolved observations have led to the discovery of a further mode of mass-loss in SS433 via a circumbinary disc. I shall present the exquisitely detailed behaviour of these modes of mass-loss before, during and after a major flare event in this object, with reference to comparable behaviour seen in similar objects.

The origin of today’s Hubble sequence and the associated galaxy scaling relations are salient issues in modern astrophysics. In this talk I overview the current state of computational galaxy formation and discuss recent advances in the field. I will focus on results from recent state-of-the-art cosmological simulations where the locations of massive star clusters are beginning to be resolved. I illustrate the sensitivity of galaxy evolution to how star formation and stellar feedback proceeds on small scales in the interstellar medium, and discuss the role of “feedback regulated" star formation. In this context I demonstrate the role of stellar feedback, and emerging galactic winds, in controlling observables such as the baryon content of galaxies, galaxy sizes, gas and stellar metallicities, and the Kennicutt-Schmidt relation over cosmic time.

I will present results from two spectroscopic surveys of the LMC supergiant HII region 30 Doradus (Tarantula Nebula), namely the VLT-FLAMES Tarantula Survey (VFTS) in which the physical, binary and kinematical properties of 800 massive stars have been obtained, plus a HST/STIS census of the central R136 ionizing cluster. I will also compare our spatially resolved stellar census with the integrated properties of the giant HII region and R136 cluster - as would be witnessed if viewed from Mpc distances, relevant to determinations of ages and stellar mass functions of extragalactic star forming regions.

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The warm dark matter (WDM) model is a promising alternative cosmological scenario. I will talk about WDM structure formation, addressing both numerical simulations and analytical approaches.

Star formation is a key problem in astronomy which impacts on galaxy formation and evolution, and sets the initial conditions for planet formation. I will talk about our current understanding of local, low-mass star formation. Firstly, how we think that bound star clusters form from smaller substructure. And also how binary observations suggest that star formation might vary from region to region even though the IMF stays the same. The conclusion is that - right now - I don't think we really understand how stars form...

Star formation is a key problem in astronomy which impacts on galaxy formation and evolution, and sets the initial conditions for planet formation. I will talk about our current understanding of local, low-mass star formation. Firstly, how we think that bound star clusters form from smaller substructure. And also how binary observations suggest that star formation might vary from region to region even though the IMF stays the same. The conclusion is that - right now - I don't think we really understand how stars form...

TBC