  We use data drawn from the DEEP2 Galaxy Redshift Survey to investigate the
relationship between local galaxy density, stellar mass, and rest-frame galaxy
color. At z ~ 0.9, we find that the shape of the stellar mass function at the
high-mass (log (M*/Msun) > 10.1) end depends on the local environment, with
high-density regions favoring more massive systems. Accounting for this stellar
mass-environment relation (i.e., working at fixed stellar mass), we find a
significant color-density relation for galaxies with 10.6 < log(M*/Msun) < 11.1
and 0.75 < z < 0.95. This result is shown to be robust to variations in the
sample selection and to extend to even lower masses (down to log(M*/Msun) ~
10.4). We conclude by discussing our results in comparison to recent works in
the literature, which report no significant correlation between galaxy
properties and environment at fixed stellar mass for the same redshift and
stellar mass domain. The non-detection of environmental dependence found in
other data sets is largely attributable to their smaller samples size and lower
sampling density, as well as systematic effects such as inaccurate redshifts
and biased analysis techniques. Ultimately, our results based on DEEP2 data
illustrate that the evolutionary state of a galaxy at z ~ 1 is not exclusively
determined by the stellar mass of the galaxy. Instead, we show that local
environment appears to play a distinct role in the transformation of galaxy
properties at z > 1.
