Data Release 11

Images from the UDS DR11 release were made available on June 28 2016. Catalogues were released on July 5 2016. The DR11 represents the final UDS release over the full 0.8 sq degrees, adding the final two years of integration. The data will be released immediately to the world, with no proprietary period for the UKIDSS consortium. In addition to the gains in exposure time, a number of major improvements have been made to the data quality and background subtraction. The median depths are given below (AB, 5σ), estimated from the rms between 2-arcsec apertures placed in source free regions.

  J   H   K   
DR11    25.6 25.1 25.3 
DR10    25.4 24.8 25.0 
DR8    24.9 24.2 24.6 
DR5    24.0 23.7 23.9 
DR3    23.7 23.5 23.7 

Seeing and depth maps

Maps showing the variations in depth and seeing are provided below:

  J   H   K   
Depth maps    text,plot text,plot text,plot 
Seeing maps    text,plot text,plot text,plot 

Image Data - full resolution

  • Full field, K-band (2.5Gb) FITS
  • Full field, K-band weight map (2.5Gb) FITS
  • Full field, H-band (2.5Gb) FITS
  • Full field, H-band weight map (2.5Gb) FITS
  • Full field, J-band (2.5Gb) FITS
  • Full field, J-band weight map (2.5Gb) FITS

Please note, by default the images above are provided in the original UKIDSS astrometric frame, calibrated to 2MASS. A fits header with the WCS updated to the GAIA EDR3 frame may be downloaded here.

NB: Pixel scale is 0.1342 arcsec. Zero points = 30.0 in each case (Vega).

Image Data - 2x2 binned

  • Full field, K-band (632Mb) FITS
  • Full field, K-band weight map (632Mb) FITS
  • Full field, H-band (632Mb) FITS
  • Full field, H-band weight map (632Mb) FITS
  • Full field, J-band (632Mb) FITS
  • Full field, J-band weight map (632Mb) FITS

NB: These images have been binned (2x2) to enable them to be viewed and manipulated on a 32bit machine or using IRAF. The images oversample the psf and are suitable for most scientific purposes. The images are provided in the original UKIDSS astrometric frame, calibrated to 2MASS. The pixel scale is 0.2684 arcsec. Zero points = 30.0 in each case (Vega).

Improvements to data quality

In addition to correcting the instrumental artefacts present in the DR8 release, the DR11 data benefit from the following changes:

  • We have identified and removed small (1-2%) systematic differences in the WFCAM zero-point between the four detectors. These systematics are apparent in earlier releases when comparing optical/IR colours in the stellar locus.
  • Background subtraction has been greatly improved for the DR11 releae. Previously the image background was slightly over-subtracted due to faint undetected sources and residuals from the outer regions of brighter detected objects. These issues were corrected by using a JHK "superstack", to probe as deep as possible, with the outer regions of sources removed from the background determination by artificially expanding the segmentation maps. This process was optimised to ensure that the outer light profiles of stars remain constant as a function of magnitude. Without these corrections, galaxies at the limit of the survey (at K=25.3) would be underestimated in flux by ~25% in 3-arcsec apertures.

Further details will be provided in the forthcoming UDS data paper (Almaini et al. in prep.).

JHK Catalogues

Catalogues were extracted using SExtractor Version 2.19.5, with detection from the K-band image. Photometry in J and H was obtained in dual image mode. Note that the catalogues below differ slightly from the official catalogues in the WFCAM Science Archive, which provide a different set of aperture magnitudes. Compared to previous data releases, the primary changes are the use of a global background estimate (manually to zero, following extensive testing) and a higher dynamic range in deblending.

Details of image masks, completeness simulations, etc, will be provided soon.

Matched catalogues, photometric redshifts, etc

A preliminary 12-band photometric catalogue with photometric redshifts and stellar masses can be found here. Further details of the multiwavelength imaging and spectroscopy in the UDS field may be found on the UDS data page.