The bright end of the galaxy luminosity function at z≃7: before the onset of mass quenching?
Year: 2014
Type: article
Abstract: We present the results of a new search for bright star-forming galaxies at z ~ 7 within the UltraVISTA DR2 and UKIDSS UDS DR10 data, which together provide 1.65 sq deg of near-infrared imaging with overlapping optical and Spitzer data. Using a full photo-z analysis to identify high-z galaxies and reject contaminants, we have selected a sample of 34 luminous (-22.7 < M_UV < -21.2) galaxies with 6.5 < z < 7.5. Crucially, the deeper imaging provided by UltraVISTA DR2 confirms all of the robust objects previously uncovered by Bowler et al. (2012), validating our selection technique. Our sample includes the most massive galaxies known at z ~ 7, with M_* ~ 10^{10} M_sun, and the majority are resolved, consistent with larger sizes (r_{1/2} ~ 1 - 1.5 kpc) than displayed by less massive galaxies. From our final sample, we determine the form of the bright end of the rest-frame UV galaxy luminosity function (LF) at z ~ 7, providing strong evidence that the bright end of the z = 7 LF does not decline as steeply as predicted by the Schechter function fitted to fainter data. We consider carefully, and exclude the possibility that this is due to either gravitational lensing, or significant contamination of our galaxy sample by AGN. Rather, our results favour a double power-law form for the galaxy LF at high z, or, more interestingly, a LF which simply follows the form of the dark-matter halo mass function at bright magnitudes. This suggests that the physical mechanism which inhibits star-formation activity in massive galaxies (i.e. AGN feedback or some other form of `mass quenching') has yet to impact on the observable galaxy LF at z ~ 7, a conclusion supported by the estimated masses of our brightest galaxies which have only just reached a mass comparable to the critical `quenching mass' of M_* = 10 ^{10.2} M_sun derived from studies of the mass function of star-forming galaxies at lower z.
DOI: 10.1093/mnras/stu449
Institutions: Royal Observatory, University of Edinburgh, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Université Pierre-et-Marie-Curie, University of Copenhagen, National Astronomical Observatory of Japan, Ehime University, University of Lisbon, Aix-Marseille Université, Laboratoire d’Astrophysique de Marseille
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Aeronautics and Space Administration, California Institute of Technology, Institute of Science and Technology Austria, Leverhulme Trust, European Commission, National Research Foundation, Danmarks Grundforskningsfond, Centre National de la Recherche Scientifique, Jet Propulsion Laboratory, Science and Technology Facilities Council, Japan Society for the Promotion of Science, Fundação para a Ciência e a Tecnologia, FP7 Space
Awards: Em busca de galáxias longínquas na época da reionização com o ALMA, Astronomy and Astrophysics at Edinburgh, Observational Study of both Forming Galaxies and Cosmic Reionization by UltraVISTA, Research in planetary formation, astrophysics, and cosmology at Bristol, G58316358, Projecto Estratégico - UI 2751 - 2011-2012, Unveiling the power of the deepest images of the Universe
OpenAlex ID: W1967532042