The fourth UltraVISTA data release

DR4 was built from the pre-processed UltraVISTA images from CASU (“The Cambridge Astronomy Survey Unit”1) observed at VISTA from 4 December, 2009 to 29 June, 2016 as available in early 2017. We downloaded 63,931 individual images. After quality control (which mainly is a rejection of images with FWHM > 1.0′′ or ellipticity > 0.1, see Sect. 4.1), we were left with 58,138 individual images that were used to create the 5 stacks for the 5 bands: Y , J , H, Ks, and NB118. The observation dates of all the individual images used can be found by inspecting the file names of the individual images which are recorded in the provenance tables