AGN environments at z<1.5 in the UKIDSS Ultra-Deep Survey
  We investigate the environments of both X-ray and radio-loud AGN within the
UKIDSS Ultra-deep Survey (UDS) using deep infrared selection to sample the
galaxy density field in the redshift range 1.0 <= z <= 1.5. Using angular
cross-correlation techniques we find that both X-ray and radio-loud AGN
preferentially reside in overdense environments. We also find that both types
of AGN cluster more strongly with those galaxies classified as `passive' rather
than those that are actively star-forming. We infer clustering scale lengths
comparable to those of passive red galaxies, suggesting that typical AGN at
these epochs reside in dark-matter halos of mass M >~ 10^13 M_sun. A closer
look at the small-scale environments of the AGN reveals that the neighbouring
galaxies of radio-loud AGN have U-B colours more skewed towards the
`green-valley' and the red sequence, whereas the neighbours of X-ray AGN show
no difference to the general galaxy population. This suggests that although
both AGN types live in overdense environments, the radio-loud AGN may be
preferentially located in more evolved cluster cores, in a similar environment
to low-powered radio AGN in the local Universe.
