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

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 17,748 Swift XRT point sources which were detected in the soft X-ray band image (0.5-2.0 keV) using wavdetect with a false positive threshold of 10^-6 (contained in Table 2 of the reference paper). The authors consider these sources to be AGN candidates.

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 June 2015 based on an electronic version of Table 2 of the reference paper, the list of Swift XRT point 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 source, using the 'SACSSP' prefix (for 'Swift Active galactic nucleus (AGN) and Cluster Survey Soft-band Point source', and the J2000.0 equatorial coordinates, e.g., 'SACSSP JHHMMSS.s+DDMMSS'. Notice that, in the original tables. the authors used a prefix of 'SACS' rather than the 'SACSSP' in this present version: the HEASARC has used used this longer prefix so as to distinguish these soft-band sources from those which were detected in the total and hard bands, as the sources in these 3 tables were all given the same prefix in their original tables. Also, the CDS Dictionary of Nomenclature of Celestial Objects has already assigned the 'SACS' prefix to another catalog.

RA
The Right Ascension of the Swift XRT 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 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 source.

BII
The Galactic Latitude of the Swift XRT source.

RA_Error
The uncertainty in the Right Ascension of the Swift XRT source, in arcseconds (converted from the units of degrees given in the original table).

Dec_Error
The uncertainty in the Declination of the Swift XRT source, in arcseconds (converted from the units of degrees given in the original table).

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

Count_Rate_Error
The uncertainty in the 0.5-2.0 keV count rate of the Swift XRT source, in ct/s.

Flux
The 0.5-2.0 keV flux of the Swift XRT source, in erg cm^-2 s^-1. The authors corrected the fluxes for the finite aperture used in the measurements, simply using the PSF for point sources. 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.

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

W1_Mag
The WISE 3.4-micron band magnitude of the closest WISE source to the Swift XRT position. The authors searched for the closest WISE source to the position of each XRT source and to random positions along a circle of radius 120 arcseconds around the XRT position. They kept the closest WISE source to both the real and random positions provided that the separation was smaller than 20 arcseconds. For each GRB field, they calculated the mean Delta in RA and Dec and variance of these means for real matches, and corrected the X-ray source astrometry if any mean offset was larger than the standard deviation of the mean offsets. The median and maximum RA corrections are 1.36 and 5.01 arcseconds, and the median and maximum Dec corrections are 1.31 and 4.36 arcseconds.

W2_Mag
The WISE 4.6-micron band magnitude of the closest WISE source to the Swift XRT position. The authors searched for the closest WISE source to the position of each XRT source and to random positions along a circle of radius 120 arcseconds around the XRT position. They kept the closest WISE source to both the real and random positions provided that the separation was smaller than 20 arcseconds. For each GRB field, they calculated the mean Delta in RA and Dec and variance of these means for real matches, and corrected the X-ray source astrometry if any mean offset was larger than the standard deviation of the mean offsets. The median and maximum RA corrections are 1.36 and 5.01 arcseconds, and the median and maximum Dec corrections are 1.31 and 4.36 arcseconds.

W3_Mag
The WISE 12-micron band magnitude of the closest WISE source to the Swift XRT position. The authors searched for the closest WISE source to the position of each XRT source and to random positions along a circle of radius 120 arcseconds around the XRT position. They kept the closest WISE source to both the real and random positions provided that the separation was smaller than 20 arcseconds. For each GRB field, they calculated the mean Delta in RA and Dec and variance of these means for real matches, and corrected the X-ray source astrometry if any mean offset was larger than the standard deviation of the mean offsets. The median and maximum RA corrections are 1.36 and 5.01 arcseconds, and the median and maximum Dec corrections are 1.31 and 4.36 arcseconds.

W4_Mag
The WISE 22-micron band magnitude of the closest WISE source to the Swift XRT position. The authors searched for the closest WISE source to the position of each XRT source and to random positions along a circle of radius 120 arcseconds around the XRT position. They kept the closest WISE source to both the real and random positions provided that the separation was smaller than 20 arcseconds. For each GRB field, they calculated the mean Delta in RA and Dec and variance of these means for real matches, and corrected the X-ray source astrometry if any mean offset was larger than the standard deviation of the mean offsets. The median and maximum RA corrections are 1.36 and 5.01 arcseconds, and the median and maximum Dec corrections are 1.31 and 4.36 arcseconds.

Offset
The offset between the Swift XRT and WISE positions, in arcseconds.

Contact Person

Questions regarding the SACSSPSCAT database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:34:18 EDT