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ROXA - ROXA (Radio-Optical-X-ray at ASDC) Blazars Catalog



Although blazars are a small fraction of the overall AGN population, they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect several thousand of objects of this type. In preparation for these missions it is necessary to identify new samples of blazars to study their multi-frequency characteristics and statistical properties. The authors have compiled a sample of objects with blazar-like properties via a cross-correlation between large radio (NVSS, ATCAPMN) and X-ray surveys (RASS) using the SDSS-DR4 and 2dF survey data to spectroscopically identify their candidates and test the validity of the selection method. They present the Radio-Optical-X-ray catalog built at ASDC (ROXA), a list of 816 objects among which 510 are confirmed blazars. Only 19% of the candidates turned out to be certainly non-blazars, demonstrating the high efficiency of our selection method. This catalog includes 173 new blazar identifications, or about 10% of all presently known blazars. The relatively high flux threshold in the X-ray energy band (given by the RASS survey) preferentially selects objects with high F_X/F_r ratio, leading to the discovery of new High Energy Peaked BL Lac (HBLs). This catalog therefore includes many new potential targets for GeV-TeV observations.

The selection method consisted of three steps: 1) a first cross-correlation between radio and X-ray surveys (the NRAO VLA Sky Survey, ATCAPMN (ATCA catalogue of compact PMN sources) and ROSAT All Sky Survey; 2) for each radio/X-ray match, optical magnitudes were retrieved from the Guide Star Catalog; 3) for all radio/optical/X-ray matches the authors calculated the X-ray to optical (alpha_ox) and radio to optical (alpha_ro) spectral slopes and took only sources with alpha_ox and alpha_ro values within the blazar area. For each object, redshift, B and G magnitudes, radio fluxes at 1.4 GHz and at 5 GHz, X-ray flux, F_X/F_r ratio, X-ray luminosity, radio luminosity, Ca H&K break and classification are given.

Catalog Bibcode



ROXA: a new multi-frequency large sample of blazars selected with SDSS and
2dF optical spectroscopy.
    Turriziani S., Cavazzuti E., Giommi P.
    <Astron. Astrophys. 472, 699 (2007)>
    =2007A&A...472..699T        (SIMBAD/NED BibCode)


This table was created by the HEASARC in November 2007 based on CDS catalog J/A+A/472/699 file catalog.dat.


The ROXA source designation, using the 'ROXASDC' prefix recommended by the CDS Dictionary of Nomenclature of Celestial Objects (replacing the 'ROXA' prefix used in the reference paper because the latter prefix has been previously used by an earlier CDS Catalog), and a numerical string based on the J2000.0 position ('JHHMMSS.s+DDMMSS.s').

The Right Ascension of the source in the selected equinox. This was given (implicitly through the position-based string part of the source name) in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table.

The Declination of the source in the selected equinox. This was given (implicitly through the position-based string part of the source name) in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

The Galactic Longitude of the source.

The Galactic Latitude of the source.

The redshift of the source.

The B_j magnitude of the source (from the 2dF GRS and QSO Surveys).

The g' (g-prime) magnitude of the source (from the SDSS Survey).

The radio flux density of the source at 1.4 GHz (from the NVSS), in mJy.

The radio flux density of the source at 5 GHz (from the North6cm, GB6 and/or PMN Catalogs), in mJy.

The ROSAT All-Sky Survey (RASS) X-fay flux of the source, in erg/s/cm^2.

The ratio of the X-ray flux to the 5-GHz radio flux of the source, in erg/s/cm^2/Jy. For objects for which no 5-GHz flux density value was available, an estimated value was caculated using F(5 GHz) = F(1.4 GHz) x (20/6)^-alpha_rm, where alpha_rm = 0.25, the assumed average value for flat-spectrum sources.

The X-ray luminosity of the source, in erg/s.

The radio luminosity of the source, in erg/s/Hz.

The Calcium II H and K break contrast value in the optical spectrum of the source.

The source classification, using the following abbreviations:

                  BLRG   = broad line radio galaxies
                  FSRQ   = flat spectrum radio quasars
                  HFSRQ  = X-ray strong flat-spectrum radio quasars
                  NELG   = narrow emission line galaxy
                  QSO RL = radio loud flat-spectrum radio quasar
                  QSO RQ = radio quiet steep-spectrum radio quasar
                  SSRQ   = radio loud steep-spectrum radio quasar
             R.G. FR II  = Radio galaxy of FR II type
  	   R.G./BL Lac = Radio Galaxy/BL transition object
  	   R.G./FSRQ   = Radio galaxy/Flat spectrum radio quasars
  	   BL Lac/FSRQ = flat spectrum radio quasars/BL transition object

This flag parameter indicates the following notes about the new objects in this catalog:

            c = new classification for those objects differently classified in
                 the literature
            o = new object (never identified before this work)
            z = objects with newly estimated redshifts

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

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 13-Nov-2007