Journal Article

How does galaxy environment matter? The relationship between galaxy environments, colour and stellar mass at <i>0.4 < z < 1</i> in the Palomar/DEEP2 survey

Ruth Grützbauch, Christopher J. Conselice, Jesús Varela, Kevin Bundy, Michael C. Cooper, Ramin Skibba and Christopher N. A. Willmer

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 2, pages 929-946
Published in print February 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI:
How does galaxy environment matter? The relationship between galaxy environments, colour and stellar mass at 0.4 < z < 1 in the Palomar/DEEP2 survey

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We present a study characterizing the environments of galaxies in the redshift range of 0.4 < z < 1 based on data from the POWIR near-infrared imaging and DEEP2 spectroscopic redshift surveys, down to a stellar mass of log M*= 10.25 M. Galaxy environments are measured in terms of nearest-neighbour densities as well as fixed aperture densities and kinematical and dynamical parameters of neighbour galaxies within a radius of 1 h−1 Mpc. We disentangle the correlations between galaxy stellar mass, galaxy colour and galaxy environment, using not only galaxy number densities, but also other environmental characteristics such as velocity dispersion, mean harmonic radius and crossing time. We find that galaxy colour and the fraction of blue galaxies depends very strongly on stellar mass at 0.4 < z < 1, while a weak additional dependence on local number densities is in place at lower redshifts (0.4 < z < 0.7). This environmental influence is most visible in the colours of intermediate-mass galaxies (10.5 < log M* < 11), whereas colours of lower- and higher-mass galaxies remain largely unchanged with redshift and environment. At a fixed stellar mass, the colour–density relation almost disappears, while the colour–stellar mass relation is present at all local densities. We find a weak correlation between stellar mass and environment at intermediate redshifts, which contributes to the overall colour–density relation. We furthermore do not find a significant correlation between galaxy colour and virial mass, i.e. parent dark matter halo mass. Galaxy stellar mass thus appears to be the crucial defining parameter for intrinsic galaxy properties such as ongoing star formation and colour.

Keywords: galaxies: evolution; galaxies: high-redshift; galaxies: kinematics and dynamics

Journal Article.  15313 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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