The stellar mass function of quiescent galaxies in 2 < z < 2.5 protoclusters
Cooper, M. C.; Muzzin, Adam; Forrest, Ben; Kodama, Tadayuki; Vulcani, Benedetta; Hirschmann, Michaela; Jablonka, Pascale; Nantais, Julie; Balogh, Michael L.; Rudnick, Gregory H.; Cerulo, Pierluigi; De Lucia, Gabriella; Demarco, Ricardo; Wilson, Gillian; Hatch, Nina A.; Noble, Allison; Maurogordato, Sophie; Finn, Rose A.; Xie, Lizhi; Castignani, Gianluca; Edward, Adit H.; Bahé, Yannick M.; Marchioni, Justin; Hewitt, Guillaume
Canada, Switzerland, Netherlands, United States, United Kingdom, Italy, Chile, France, Japan, China
Abstract
We present an analysis of the galaxy stellar mass function (SMF) of 14 known protoclusters between 2.0 < z < 2.5 in the COSMOS field, down to a mass limit of 109.5 M⊙. We use existing photometric redshifts with a statistical background subtraction, and consider star-forming and quiescent galaxies identified from (NUV - r) and (r - J) colours separately. Our fiducial sample includes galaxies within 1 Mpc of the cluster centres. The shape of the protocluster SMF of star-forming galaxies is indistinguishable from that of the general field at this redshift. Quiescent galaxies, however, show a flatter SMF than in the field, with an upturn at low mass, though this is only significant at ~2σ. There is no strong evidence for a dominant population of quiescent galaxies at any mass, with a fraction <15 per cent at 1σ confidence for galaxies with log M*/M⊙ < 10.5. We compare our results with a sample of galaxy groups at 1 < z < 1.5, and demonstrate that a significant amount of environmental quenching must take place between these epochs, increasing the relative abundance of high-mass ($\rm M_{\ast } \gt 10^{10.5} {\rm M}_{\odot }$) quiescent galaxies by a factor ≳ 2. However, we find that at lower masses ($\rm M_{\ast } \lt 10^{10.5} {\rm M}_{\odot }$), no additional environmental quenching is required.