The bright end of the galaxy luminosity function at z 7 from the VISTA VIDEO survey

Abstract

We have conducted a search for z 7 Lyman-break galaxies over 8.2 deg2 of near-infrared imaging from the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey in the XMM-Newton-Large Scale Structure (XMM-LSS) and the Extended Chandra Deep Field-South (ECDF-S) fields. Candidate galaxies were selected from a full photometric redshift analysis down to a Y + J depth of 25.3 (5σ), utilizing deep auxiliary optical and Spitzer/Infrared Array Camera (IRAC) data to remove brown dwarf and red interloper galaxy contaminants. Our final sample consists of 28 candidate galaxies at 6.5 ≤ z ≤ 7.5 with-23.5 ≤ MUV ≤-21.6. We derive stellar masses of 9.1 ≤ log10(Mâ/MâŠ) ≤ 10.9 for the sample, suggesting that these candidates represent some of the most massive galaxies known at this epoch. We measure the rest-frame ultraviolet (UV) luminosity function (LF) at z 7, confirming previous findings of a gradual decline in number density at the bright end (MUV 5 samples, our results further support little evolution in the very bright end of the rest-frame UV LF from z = 5-10, potentially signalling a lack of mass quenching and/or dust obscuration in the most massive galaxies in the first Gyr.