Browse
this table...

SACSSESCAT - Swift AGN & Cluster Survey (SACS) Soft-Band (0.5-2 keV) Extended Source Catalog

HEASARC
Archive

Overview

The Swift Active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg2 of Swift X-ray Telescope (XRT) serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 x 10-15 erg cm-2 s-1) and medium area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. In the reference paper, a catalog of 22,563 point sources and 442 extended sources, and the number counts of the AGN and galaxy cluster populations are presented. 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. The authors use Wide-field Infrared Survey Explorer (WISE) mid-infrared(MIR) colors to classify the sources. For AGNs, they 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 (0.5-2.0 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 followup observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters.

This HEASARC table contains the list of 442 Swift XRT extended sources which were detected in the soft X-ray band image (0.5-2 keV) and contained in Table 4 of the reference paper. The authors defined the extended source catalog as those sources with S/N >= 4 and a minimum net photon count of 20 that are more than 3 sigma from the mean size of point sources for both their off-axis angle and S/N. The authors consider these extended sources to be candidate clusters of galaxies.


Catalog Bibcode

2015ApJS..218....8D

References

The Swift AGN and Cluster Survey. I. Number counts of AGNs and Galaxy Clusters
    Dai X., Griffin R.D., Kochanek C.S., Nugent J.M., Bregman J.N.
   <Astrophys. J. Suppl., 218, 8 (2015)>
   =2015ApJS..218....8D    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in July 2015 based on an electronic version of Table 4 of the reference paper, the list of Swift XRT extended sources detected in the soft X-ray (0.5-2 keV) band, which was obtained from the ApJS web site.

Parameters

Name
The name of the Swift XRT extended source, using the 'SWCL' prefix (for 'Swift Cluster of Galaxies', and the J2000.0 equatorial coordinates, e.g., 'SWCL JHHMMSS.s+DDMMSS'

RA
The Right Ascension of the Swift XRT extended source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-4 degrees in the original table.

Dec
The Declination of the Swift XRT extended source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-4 degrees in the original table.

LII
The Galactic Longitude of the Swift XRT extended source.

BII
The Galactic Latitude of the Swift XRT extended source.

Core_Size
The core size Rc of the beta model fit to the Swift XRT extended source, in arcseconds. The authors corrected the fluxes for the finite aperture used in the measurements. For these extended sources, they assumed a beta = 0.6, Rc = 0.1 Mpc beta model (e.g., Sanderson et al. 2003, MNRAS, 340, 989) at the typical cluster redshift of z = 0.5.

Extent
The angular extent of the Swift XRT extended source, in arcseconds.

Count_Rate
The 0.5-2 keV count rate of the Swift XRT extended source, in ct/s.

Count_Rate_Error
The uncertainty in the 0.5-2 keV count rate of the Swift XRT extended source, in ct/s.

Flux
The 0.5-2 keV flux of the Swift XRT extended source, in erg cm-2 s-1. The authors corrected the fluxes for the finite aperture used in the measurements, using a beta model fit to the Swift XRT extended source with beta = 0.6 and Rc = 0.1 Mpc (e.g., Sanderson et al. 2003, MNRAS, 340, 989) at the typical cluster redshift of z = 0.5, and estimating the total flux within 2 Mpc. This typically increased the fluxes by a factor of 1.3. They assumed a T = 5 keV, 0.4 solar metallicity plasma spectrum at z = 0.5 to correct their fluxes for Galactic absorption using the Dickey and Lockman (1990, ARAA, 28, 215) estimates.

Bck_Count_Rate
The background count rate in the 0.5-2 keV band in the vicinity of the Swift XRT extended source, in counts s-1 arcmin-2.

Off_Axis
The off-axis angle of the Swift XRT extended source from the nominal pointing direction, in arcminutes.

Exposure
The total exposure of the merged reprocessed event file for the GRB observations in which the Swift XRT extended source was located, in seconds.

GRB_Field
The name of the GRB field in which the Swift XRT extended source was located.


Contact Person

Questions regarding the SACSSESCAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 6-Jul-2015