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The 10k zCOSMOS: Morphological Transformation of Galaxies in the Group Environment Since z ~1

Kovač, K. and Scarlata, C. and Scoville, N. Z. (2010) The 10k zCOSMOS: Morphological Transformation of Galaxies in the Group Environment Since z ~1. Astrophysical Journal, 718 (1). pp. 86-104. ISSN 0004-637X.

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We study the evolution of galaxies inside and outside of the group environment since z = 1 using a large well-defined set of groups and galaxies from the zCOSMOS-bright redshift survey in the COSMOS field. The fraction of galaxies with early-type morphologies increases monotonically with M_B luminosity and stellar mass and with cosmic epoch. It is higher in the groups than elsewhere, especially at later epochs. The emerging environmental effect is superposed on a strong global mass-driven evolution, and at z ~ 0.5 and log(M _*/M_⊙) ~ 10.2, the "effect" of the group environment is equivalent to (only) about 0.2 dex in stellar mass or 2 Gyr in time. The stellar mass function of galaxies in groups is enriched in massive galaxies. We directly determine the transformation rates from late to early morphologies, and for transformations involving color and star formation indicators. The transformation rates are systematically about twice as high in the groups as outside, or up to three to four times higher correcting for infall and the appearance of new groups. The rates reach values as high as 0.3-0.7 Gyr^(–1) in the groups (for masses around the crossing mass 10^(10.5) M_⊙), implying transformation timescales of 1.4-3 Gyr, compared with less than 0.2 Gyr^(–1), i.e., timescales >5 Gyr, outside of groups. All three transformation rates decrease at higher stellar masses, and must also decrease at lower masses below 10^(10) M _⊙ which we cannot probe well. The rates involving color and star formation are consistently higher than those for morphology, by a factor of about 50%. Our conclusion is that the transformations that drive the evolution of the overall galaxy population since z ~ 1 must occur at a rate two to four times higher in groups than outside of them.

Item Type:Article
Related URLs:
Scarlata, C.0000-0002-9136-8876
Scoville, N. Z.0000-0002-0438-3323
Additional Information:© 2010 The American Astronomical Society. Received 2009 August 24; accepted 2010 March 3; published 2010 June 28. Based on observations obtained at the European Southern Observatory (ESO) Very Large Telescope (VLT), Paranal, Chile, as part of the Large Program 175.A-0839 (the zCOSMOS Spectroscopic Redshift Survey). This work has been supported in part by a grant from the Swiss National Science Foundation and by grant ASI/COFIS/ WP3110I/026/07/0.
Funding AgencyGrant Number
Swiss National Science FoundationASI/COFIS/WP3110I/026/07/0
Subject Keywords:galaxies: clusters: general; galaxies: evolution; galaxies: high-redshift; galaxies: luminosity function, mass function; galaxies: structure
Issue or Number:1
Classification Code:PACS: 95.80.+p; 98.62.Py; 98.65.Cw; 98.62.Qz; 98.62.Lv; 98.62.Ai
Record Number:CaltechAUTHORS:20100817-150115114
Persistent URL:
Official Citation:K. Kovač et al 2010 ApJ 718 86 doi: 10.1088/0004-637X/718/1/86
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19483
Deposited By: Tony Diaz
Deposited On:17 Aug 2010 23:51
Last Modified:03 Oct 2019 01:57

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