The Neil Gehrels Swift Observatory

The Swift AGN & Cluster Survey

Dai et al. (2015) published this catalog of sources seen with the XRT (ADS).


The Swift active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding γ-ray bursts to provide a medium depth (4 x 10‑15 erg cm‑2 s‑1) and area survey filling the gap between deep, narrow iChandra/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 Wide-field Infrared Survey Explorer mid-infrared (MIR) colors to classify the sources. For AGNs we can roughly separate the point sources into MIR-red and MIR-blue AGNs, 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.


Xinyu Dai1, Rhiannon D. Griffin1, Christopher S. Kochanek2, Jenna M. Nugent1, and Joel N. Bregman3

1Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA
2Department of Astronomy and the Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, OH 43210, USA
3Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA

Data Access

The SACS survey produced four source catalogs available at the HEASARC.

  1. SACS Hard-Band Point Source Catalog (sacshpscat)
  2. SACS Soft-Band Extended Source Catalog (sacssescat)
  3. SACS Soft-Band Point Source Catalog (sacsspscat)
  4. SACS Total-Band Point Source Catalog (sacstpscat)