Thursday, 21 March 2024
Two undergraduate students from the University of Nottingham are part of an international team who have revealed that a brilliant supermassive black hole is not living up to expectations in a new study using NASA’s Chandra X-ray Observatory.
The students undertook the research, published in Monthly Notices of the Royal Astronomical Society, as a final year project for their Physics degree. The study revealed that although the supermassive black hole is responsible for high levels of radiation and powerful jets, this giant black hole is not as influential as many of its counterparts in other galaxies.
Dr Helen Russell led the study and supervised the students, she said: “This is an exciting result and it’s a fantastic achievement for two undergraduate students to co-author a published study.
“We have found that the quasar in our study appears to have relinquished much of the control imposed by more slowly growing black holes and the black hole’s appetite is not matched by its influence.”
Thomas Braben and Lucy Clews at their graduation
Thomas Braben and Lucy Clews used the Chandra X-ray Observatory to look at the closest quasar to Earth that is in a cluster of galaxies. Known as H1821+643, this quasar is about 3.4 billion light-years from Earth. Quasars are a rare and extreme class of supermassive black holes that are furiously pulling material inwards, producing intense radiation and sometimes powerful jets.
Much less is known about how much influence quasars in galaxy clusters have on their surroundings.
Chandra was used to study the hot gas that H1821+643 and its host galaxy are shrouded in. The bright X-rays from the quasar, however, made it difficult to study the weaker X-rays from the hot gas.
“We had to carefully remove the X-ray glare to reveal what the black hole’s influence is,” said co-author Paul Nulsen of the Centre for Astrophysics | Harvard & Smithsonian. “We could then see that it’s actually having little effect on its surroundings.”
Using Chandra, the team found that the density of gas near the black hole in the center of the galaxy is much larger, and the gas temperatures much smaller, than in regions farther away. Scientists expect the hot gas to behave like this when there are little or no sources of energy (typically outbursts from a black hole) to prevent the hot gas from cooling down and flowing towards the center of the cluster.
“The giant black hole is generating a lot less heat than most of the others in the centers of galaxy clusters,” said co-author Lucy Clews who is now at Open University in the UK. “This allows the hot gas to rapidly cool down and form new stars, and also act as a fuel source for the black hole.”
The researchers determined that hot gas equivalent to about 3000 times the mass of the Sun per year is cooling to the point that it is no longer visible in X-rays. This rapid cooling can easily supply enough material for the 120 solar masses of new stars observed to form in the host galaxy every year, and the 40 Sun’s consumed by the black hole each year.
The team also examined the possibility that the radiation from the quasar is directly causing the cluster’s hot gas to cool down. This involves photons of light from the quasar colliding with electrons in the hot gas, causing the photons to become more energetic and the electrons to lose energy and cool down. The team’s study showed that this type of cooling is probably occurring in the cluster containing H1821+643 but is much too weak to explain the large amount of gas cooling seen.
“While this black hole may be underachieving by not pumping heat into its environment, the current state of affairs will likely not last forever,” said co-author Thomas Braben, PhD at the University of Nottingham. “Eventually the rapid fuel intake by the black hole should increase the power of its jets and strongly heat the gas. The growth of the black hole and its galaxy should then drastically slow down.”
I am ecstatic about my work being used in this way! It is wonderful to be featured on an academic paper and it only makes me want to get more work done for further publications! It is very rare to be featured as even many PhD students don't get their names properly published before finishing
I would never have imagined that my name would be on a paper this early in my career, I hope it can inspire other students to also take up Astronomy.
Story credits
More information is available from Professor Helen Russell on Helen.Russell@nottingham.ac.uk
Main image caption: In the center of this image is the quasar H1821+643, a rapidly growing supermassive black hole that astronomers have found is underachieving, despite producing intense radiation and a jet of particles seen in radio data from the Very Large Array (red). Located in the middle of a cluster of galaxies, H1821+643 is surrounded by huge quantities of hot gas detected in X-rays by Chandra (blue). The high temperatures and densities of the hot gas around the quasar shows that the black hole is having a weaker impact on its host galaxy than many of its other counterparts in other galaxy clusters. H1821+643 is the closest quasar to Earth in a cluster of galaxies. It is located 3.4 billion light-years from Earth and the image is about a million light-years across at the distance of the quasar.
Credit:X-ray: NASA/CXC/Univ. of Nottingham/H. Russell et al.; Radio: NSF/NRAO/VLA; Image Processing: NASA/CXC/SAO/N. Wolk
Notes to editors:
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Ranked 32 in Europe and 16th in the UK by the QS World University Rankings: Europe 2024, the University of Nottingham is a founding member of the Russell Group of research-intensive universities. Studying at the University of Nottingham is a life-changing experience, and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement.
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