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