THE CLUSTER AND FIELD GALAXY ACTIVE GALACTIC NUCLEUS FRACTION AT z=1-1.5: EVIDENCE FOR A REVERSAL OF THE LOCAL ANTICORRELATION BETWEEN ENVIRONMENT AND AGN FRACTION

The fraction of cluster galaxies that host luminous active galactic nuclei (AGNs) is an important probe of AGN fueling processes, the cold interstellar medium at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M >= 10(14) M-circle dot) at 1 < z < 1.5 selected from the Spitzer/IRAC Shallow Cluster Survey, as well as the field fraction in the immediate vicinity of these clusters, and combine these data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z similar to 3. We estimate that the cluster AGN fraction at 1 < z < 1.5 is f(A) = 3.0(-1.4)(+2.4)% for AGNs with a rest-frame, hard X-ray luminosity greater than L-X,L- H >= 10(44) erg s(-1). This fraction is measured relative to all cluster galaxies more luminous than M-3.6*(z)+ 1, where M-3.6*(z) is the absolute magnitude of the break in the galaxy luminosity function at the cluster redshift in the IRAC 3.6 mu m bandpass. The cluster AGN fraction is 30 times greater than the 3 sigma upper limit on the value for AGNs of similar luminosity at z similar to 0.25, as well as more than an order of magnitude greater than the AGN fraction at z similar to 0.75. AGNs with L-X,L- H >= 10(43) erg s(-1) exhibit similarly pronounced evolution with redshift. In contrast to the local universe, where the luminous AGN fraction is higher in the field than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1 < z < 1.5. This is evidence that the cluster AGN population has evolved more rapidly than the field population from z similar to 1.5 to the present. This environment-dependent AGN evolution mimics the more rapid evolution of star-forming galaxies in clusters relative to the field.