The SWIFT AGN and Cluster Survey I: Number Counts of AGN and Galaxy
  Clusters
  The Swift AGN and Cluster Survey (SACS) uses 125 deg^2 of Swift XRT
serendipitous fields with variable depths surrounding gamma-ray bursts to
provide a medium depth (4e-15 erg/s/cm^2) and area survey filling the gap
between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT
surveys. Here we present a catalog of 22,563 point sources and 442 extended
sources and examine the number counts of the AGN and galaxy cluster
populations. SACS provides excellent constraints on the AGN number counts at
the bright end with negligible uncertainties due to cosmic variance, and these
constraints are consistent with previous measurements. We use Wise mid-infrared
(MIR) colors to classify the sources. For AGN we can roughly separate the point
sources into MIR-red and MIR-blue AGN, finding roughly equal numbers of each
type in the soft X-ray band (0.5-2 keV), but fewer MIR-blue sources in the hard
X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from
cosmic variance, are also consistent with previous surveys but span a much
larger continuous flux range. Deep optical or IR follow-up observations of this
cluster sample will significantly increase the number of higher redshift (z >
0.5) X-ray-selected clusters.
