Galaxy Clusters in the IRAC Dark Field II: Mid-IR Sources
  We present infrared luminosities, star formation rates, colors, morphologies,
locations, and AGN properties of 24 micron-detected sources in photometrically
detected high-redshift clusters in order to understand the impact of
environment on star formation and AGN evolution in cluster galaxies. We use
three newly-identified z=1 clusters selected from the IRAC dark field; the
deepest ever mid-IR survey with accompanying, 14 band multiwavelength data
including deep HST imaging and deep wide-area Spitzer MIPS 24 micron imaging.
We find 90 cluster members with MIPS detections within two virial radii of the
cluster centers, of which 17 appear to have spectral energy distributions
dominated by AGN and the rest dominated by star formation. We find that 43 of
the star forming are luminous infrared galaxies (LIRGs). The majority of
sources (81%) are spirals or irregulars. A large fraction (at least 25%) show
obvious signs of interactions. The MIPS -detected member galaxies have varied
spatial distributions as compared to the MIPS-undetected members with one of
the three clusters showing SF galaxies being preferentially located on the
cluster outskirts, while the other 2 clusters show no such trend. Both the AGN
fraction and the summed SFR of cluster galaxies increases from z=0 to 1, at a
rate that is a few times faster in clusters than over the same redshift range
in the field. Cluster environment does have an effect on the evolution of both
AGN fraction and SFR from redshift one to the present, but does not effect the
infrared luminosities or morphologies of the MIPS sample. Star formation
happens in the same way regardless of environment making MIPS sources look the
same in the cluster and field, however the cluster environment does encourage a
more rapid evolution with time as compared to the field.
