Galaxy Environments in the UKIDSS Ultra Deep Survey (UDS)
  We present a study of galaxy environments to z~2, based on a sample of over
33,000 K-band selected galaxies detected in the UKIDSS Ultra Deep Survey (UDS).
The combination of infrared depth and area in the UDS allows us to extend
previous studies of galaxy environment to z>1 without the strong biases
associated with optical galaxy selection. We study the environments of galaxies
divided by rest frame (U-B) colours, in addition to `passive' and
`star-forming' subsets based on template fitting. We find that galaxy colour is
strongly correlated with galaxy overdensity on small scales (<1Mpc diameter),
with red/passive galaxies residing in significantly denser environments than
blue/star-forming galaxies to z~1.5. On smaller scales (<0.5Mpc diameter) we
also find a relationship between galaxy luminosity and environment, with the
most luminous blue galaxies at z~1 inhabiting environments comparable to red,
passive systems at the same redshift. Monte Carlo simulations demonstrate that
these conclusions are robust to the uncertainties introduced by photometric
redshift errors.
