The Cosmic Evolution of AGN in galaxy clusters
  We present the surface density of luminous active galactic nuclei (AGN)
associated with a uniformly selected galaxy cluster sample identified in the
8.5 square degree Bootes field of the NOAO Deep Wide-Field Survey. The clusters
are distributed over a large range of redshift (0 < z < 1.5) and we identify
AGN using three different selection criteria: mid-IR color, radio luminosity,
and X-ray luminosity. Relative to the field, we note a clear overdensity of the
number of AGN within 0.5 Mpc of the cluster centers at z > 0.5. The amplitude
of this AGN overdensity increases with redshift. Although there are significant
differences between the AGN populations probed by each selection technique, the
rise in cluster AGN surface density generally increases more steeply than that
of field quasars. In particular, X-ray selected AGN are at least three times
more prevalent in clusters at 1 < z < 1.5 compared to clusters at 0.5 < z < 1.
This effect is stronger than can be explained by the evolving median richness
of our cluster sample. We thus confirm the existence of a Butcher-Oemler type
effect for AGN in galaxy clusters, with the number of AGN in clusters
increasing with redshift.
