The DEEP2 galaxy redshift survey: evolution of the colour–density relation at 0.4 < z < 1.35 |
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| Authors: | Michael C Cooper Jeffrey A Newman † Alison L Coil † Darren J Croton Brian F Gerke Renbin Yan Marc Davis S M Faber Puragra Guhathakurta David C Koo Benjamin J Weiner Christopher N A Willmer ‡ |
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| Institution: | Department of Astronomy, University of California at Berkeley, Mail Code 3411, Berkeley, CA 94720, USA;Lawrence Berkeley National Laboratory, 1 Cyclotron Road Mail Stop 50-208, Berkeley, CA 94720, USA;Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA;Department of Physics, University of California at Berkeley, Mail Code 7300, Berkeley, CA 94720, USA;UCO/Lick Observatory, UC Santa Cruz, Santa Cruz, CA 95064, USA;Department of Astronomy, University of Maryland, College Park, MD 20742, USA |
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| Abstract: | Using a sample of 19 464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy colour and environment at 0.4 < z < 1.35 . We find that the fraction of galaxies on the red sequence depends strongly on local environment out to z > 1 , being larger in regions of greater galaxy density. At all epochs probed, we also find a small population of red, morphologically early-type galaxies residing in regions of low measured overdensity. The observed correlations between the red fraction and local overdensity are highly significant, with the trend at z > 1 detected at a greater than 5σ level. Over the entire redshift regime studied, we find that the colour–density relation evolves continuously, with red galaxies more strongly favouring overdense regions at low z relative to their red-sequence counterparts at high redshift. At z ? 1.3 , the red fraction only weakly correlates with overdensity, implying that any colour dependence to the clustering of ～ L * galaxies at that epoch must be small. Our findings add weight to existing evidence that the build-up of galaxies on the red sequence has occurred preferentially in overdense environments (i.e. galaxy groups) at z ? 1.5 . Furthermore, we identify the epoch ( z ～ 2) at which typical ～ L * galaxies began quenching and moved on to the red sequence in significant number. The strength of the observed evolutionary trends at 0 < z < 1.35 suggests that the correlations observed locally, such as the morphology–density and colour–density relations, are the result of environment-driven mechanisms (i.e. 'nurture') and do not appear to have been imprinted (by 'nature') upon the galaxy population during their epoch of formation. |
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| Keywords: | galaxies: evolution galaxies: fundamental parameters galaxies: high-redshift galaxies: statistics large-scale structure of Universe |
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