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CGRABS - Candidate Gamma-Ray Blazar Survey Source Catalog



The authors have constructed a uniform all-sky survey of bright blazars, selected primarily by their flat radio spectra, that is designed to provide a large catalog of likely gamma-ray active galactic nuclei (AGNs). The defined sample, the Candidate Gamma-Ray Blazar Survey (CGRaBS) source catalog, has 1625 targets with radio and X-ray properties similar to those of the EGRET blazars, spread uniformly across the |b| > 10 degrees sky. They also report progress toward optical characterization of the sample; of objects with known red magnitude R < 23, 85% have been classified and 81% have measured redshifts. One goal of this program is to focus attention on the most interesting (e.g., high-redshift, high-luminosity, etc.) sources for intensive multi-wavelength study during the observations by the Large Area Telescope (LAT) on the Gamma-Ray Large-Area Space Telescope (GLAST) satellite observatory.

Catalog Bibcode



CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
  Healey, Stephen E.; Romani, Roger W.; Cotter, Garret; Michelson, Peter F.;
  Schlafly, Edward F.; Readhead, Anthony C. S.; Giommi, Paolo; Chaty, Sylvain;
  Grenier, Isabelle A.; Weintraub, Lawrence C.
  =Astrophysical Journal Supplement Series, Volume 175, Issue 1, pp. 97-104.


This table was created by the HEASARC in April 2008 based on an electronic version of Table 2 of the reference paper obtained from the electronic ApJS web site.


This parameter is a unique name identifying CGRaBS sources using the J2000.0 positional-based convention for names and the CGRaBS prefix, as registered with the CDS Dictionary of Nomenclature of Celestial Objects.

The Right Ascension of the radio source in the selected equinox. This was given in J2000 decimal degree coordinates and to a precision of 0.01 seconds of time in the original table.

The Declination of the radio source in the selected equinox. This was given in J2000 decimal degree coordinates and to a precision of 0.1 arcseconds in the original table.

The Galactic Longitude of the radio source.

The Galactic Latitude of the radio source.

The flux density of the radio source at 8.4 GHz, in mJy.

The figure of merit (FoM) of the radio source, being a measure of the combined probability that the radio source will be similar to those blazar sources detected as EGRET gamma-ray sources. This table contains only the best such sources having FoM > 0.04. This parameter is discussed in some detail in Section 2 of the reference paper.

This flag parameter is set to "X" to indicate that the source would not satisfy the FoM cutoff if its X-ray flux were ignored (see Section 2 of the reference paper).

This parameter is a limit flag for the R magnitude of the optical counterpart to the radio source.

The R-band magnitude of the optical counterpart to the radio source.

The nominal Galactic extinction in the R band in the direction of the radio source, derived from the Schlegel et al. (1998, ApJ, 500, 525) maps.

The source classification, derived as discussed in Section 3.2 of the reference paper, using the following abbreviations:

  AGN   -  Active Galactic Nucleus (low-luminosity, broad-line blazar)
  BLL   -  BL Lac (continuum-dominated blazar)
  FSRQ  -  Flat spectrum radio quasar (luminous, broad-line blazar)
  GALAXY-  Source with small line equivalent widths but large H/K break contrast
  NLRG  -  Narrow-line (< 1000 km/s) radio galaxy
  PN    -  Planetary nebula

The redshift of the optical counterpart to the radio source.

This flag parameter is set to ':' to indicate that there is some uncertainty in the quoted redshift value.

This parameter indicates the reference for the quoted redshift, as follows:

    V  -  Veron Quasar Catalog (12th Edition)
    S  -  SDSS DR5 Quasar Catalog
    N  -  NED
    I  -  Simbad
    C  -  CGRaBS spectroscopy

The HEASARC Browse object classification, based on the value of the source_type parameter.

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 19-Mar-2015