Measuring the Dark Matter Halo Mass of X-ray AGN at z~1 using
  photometric redshifts
  Data from the AEGIS, COSMOS and ECDFS surveys are combined to infer the bias
and dark matter halo mass of moderate luminosity [LX(2-10 keV) = 42.9 erg s-1]
X-ray AGN at z~1 via their cross-correlation function with galaxies. In
contrast to standard cross-correlation function estimators, we present a method
that requires spectroscopy only for the AGN and uses photometric redshift
probability distribution functions for galaxies to determine the projected
real-space AGN/galaxy cross-correlation function. The estimated dark matter
halo mass of X-ray AGN in the combined AEGIS, COSMOS and ECDFS fields is
~13h-1M_solar, in agreement with previous studies at similar redshift and
luminosity ranges. Removing from the sample the 5 per cent of the AGN
associated with X-ray selected groups results in a reduction by about 0.5 dex
in the inferred AGN dark matter halo mass. The distribution of AGN in dark
matter halo mass is therefore skewed and the bulk of the population lives in
moderate mass haloes. This result favour cold gas accretion as the main channel
of supermassive black hole growth for most X-ray AGN.
