The SEDs, Host Galaxies and Environments of Variability Selected AGN in
  GOODS-S
  Variability selection has been proposed as a powerful tool for identifying
both low-luminosity AGN and those with unusual SEDs. However, a systematic
study of sources selected in such a way has been lacking. In this paper, we
present the multi-wavelength properties of the variability selected AGN in
GOODS South. We demonstrate that variability selection indeed reliably
identifies AGN, predominantly of low luminosity. We find contamination from
stars as well as a very small sample of sources that show no sign of AGN
activity, their number is consistent with the expected false positive rate. We
also study the host galaxies and environments of the AGN in the sample.
Disturbed host morphologies are relatively common. The host galaxies span a
wide range in the level of ongoing star-formation. However, massive star-bursts
are only present in the hosts of the most luminous AGN in the sample. There is
no clear environmental preference for the AGN sample in general but we find
that the most luminous AGN on average avoid dense regions while some
low-luminosity AGN hosted by late-type galaxies are found near the centres of
groups. AGN in our sample have closer nearest neighbours than the general
galaxy population. We find no indications that major mergers are a dominant
triggering process for the moderate to low luminosity AGN in this sample. The
environments and host galaxy properties instead suggest secular processes, in
particular tidal processes at first passage and minor mergers, as likely
triggers for the objects studied. This study demonstrates the strength of
variability selection for AGN and gives first hints at possibly triggering
mechanisms for high-redshift low luminosity AGN.
