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DXRBS - Deep X-Ray Radio Blazar Survey

 HEASARC
Archive

Overview

Perlman et al. (1998) have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter (PSPC) data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, and restricting their candidate list to serendipitous flat radio spectrum sources (i.e., those with a radio spectral alpha_r <= 0.70, where S_nu ~ nu^-alpha_r). The authors state that their survey has been found to be ~95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of their first 85 identifications) and BL Lacertae objects (22 of their first 85 identifications), a figure that is comparable to or greater than that achieved by other radio and X-ray survey techniques. They further state that the identifications presented here show that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of X-ray luminosity - radio luminosity (L_X, L_R) parameter space within which large fractions of the blazar population lie.

The authors believe that a particularly important finding is the identification of a large population of FSRQs (>~25% of DXRBS FSRQs) with ratios of X-ray to radio luminosity >~10^-6 (alpha_rx <~ 0.78). In addition, as a result of its greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in complete samples with 5 GHz (radio) luminosities between 10^31.5 and 10^33.5 ergs s^-1 Hz^-1, and it fills in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS is the very first sample to contain statistically significant numbers of blazars at low luminosities, approaching what should be the lower end of the FSRQ luminosity function.

This catalog contains data for 85 indentified sources meeting the authors selection criteria. A number of sources were serendipitously observed by ROSAT on more than one occasion; for completeness, the WGACAT positions for these multiply observed sources are listed separately, resulting in 102 entries in this catalog (71 sources with 1 X-ray observation, 11 sources with 2 X-ray observations, and 3 sources with 3 X-ray observations).

Catalog Bibcode

1998AJ....115.1253P

References

Perlman, E.S., Padovani, P., Giommi, P., Sambruna, R.M., Jones, L.R., Tzioumis, A., and Reynolds, J. 1998, AJ, 115, 1253

Provenance

This database was created by the HEASARC in March 1999 based on tables provided by P. Padovani.

Parameters

Name
The name of the object, using the standard IAU nomenclature scheme with the prefix of WGACAT and the J2000 co-ordinates as the kernel.

RA
The right ascension of the X-ray source in the WGACAT database, in the selected equinox (notice that the co-ordinates in the original input table were in J2000).

Dec
The declination of the X-ray source in the WGACAT database, in the selected equinox (notice that the co-ordinates in the original input table were in J2000).

LII
The galactic longitude of the X-ray source.

BII
The galactic latitude of the X-ray source.

Ctr_Offset
The offset of the X-ray source identified as a blazar or FSRQ from the center of the PSPC field of view, in arcminutes.

Error_Radius
The error radius of the WGACAT X-ray source, in arcseconds.

Radio_RA
The right ascension of the radio source, as taken from either the PMN or the GB6 Catalogs, in J2000 co-ordinates: notice that changing the selected equinox in BROWSE/W3Browse does not affect this co-ordinate's equinox which is fixed at J2000.

Radio_Dec
The declination of the radio source, as taken from either the PMN or the GB6 Catalogs, in J2000 co-ordinates: notice that changing the selected equinox in BROWSE/W3Browse does not affect this co-ordinate's equinox which is fixed at J2000.

Optical_RA
The right ascension of the optical counterpart, in J2000 co-ordinates: notice that changing the selected equinox in BROWSE/W3Browse does not affect this co-ordinate's equinox which is fixed at J2000.

Optical_Dec
The declination of the optical counterpart, in J2000 co-ordinates: notice that changing the selected equinox in BROWSE/W3Browse does not affect this co-ordinate's equinox which is fixed at J2000.

Source
The primary survey/catalog source for the accurate positioning (identification) of the blazar/FSRQ, using the following acronyms: 


           APM    Automatic Plate Measuring versions of the Palomar and UK
                  Schmidt Sky Catalogs
           ATCA   A snapshot survey with the Australia Telescope Compact Array
                  that was conducted by the authors at 3.6 and 6 cm
           FIRST  Faint Images of the Radio Sky at Twenty centimeters
                  (Becker et al. 1995, ApJS, 450, 559)
           GB6    The Green Bank 6-cm Survey Catalog (Gregory et al. 1996,
                  ApJS, 103, 427)
           NVSS   NRAO VLA Sky Survey (Condon et al. 1998, AJ, 115, 1693)
           OPT    Optical identification
           PMN    Parkes-MIT-NRAO Survey (e.g., Wright et al. 1996,
                  ApJS, 103, 145, and papers cited therein)
           TEXAS  Texas Survey (Douglas et al. 1996, AJ, 111, 1945)

Offset_X_Opt
The offset in arcseconds between the X-ray and optical positions.

Ctrpart_Error
The uncertainty in the position of the optical counterpart, in arcseconds.

Cum_Error
The root-mean-square sum of the X-ray and optical positional uncertainties (error_radius and ctrpart_error, respectively), in arcseconds.

Offset_X_Opt_Sig
The ratio of the offset in arcseconds between the X-ray and optical positions (offset_x_opt) to the root-mean-square sum of the X-ray and optical positional uncertainties (cum_error), i.e., the X-ray vs. optical offset in multiples of sigma.

Count_Rate
The observed ROSAT PSPC count rate for the source, in counts per second.

Fx
The observed ('absorbed') 0.1 - 2.0 keV X-ray flux for the source (i.e., not corrected for Galactic absorption) in erg/cm^2/sec, using a conversion factor that was derived from the ROSAT PSPC count rate using the observed hardness ratio and an assumed Galactic hydrogen column density.

Fx_Dens_1keV
The 1 keV flux density for the source, corrected for Galactic absorption, in microJanskies, using a conversion factor that was derived from the ROSAT PSPC count rate using the observed hardness ratio and an assumed Galactic hydrogen column density.

Log_Fx_Fradio
The ratio of the 'unabsorbed' 0.1 - 2.0 keV X-ray flux (i.e., corrected for Galactic absorption) to the 6-cm radio flux density, in erg/cm^2/sec/Jy.

Flux_6_cm
The observed 6-cm (5-GHz) flux density in milliJanskies of the radio counterpart.

Spectral_Index
The radio spectral index of the object.

Bmag_Sign
This parameter is set to '>' if only an upper limit is available.

Bmag
The blue (O) magnitude of the optical counterpart as measured from the Palomar or UK Schmidt Surveys.

Rmag_Sign
This parameter is set to '>' if only an upper limit is available.

Rmag
The red (E) magnitude of the optical counterpart as measured from the Palomar or UK Schmidt Surveys.

Object_Type
The object type as given by the authors and falling into one of three categories: 

              FSRQ       Flat-Sepctrum Radio-loud Quasar
              BL LAC     BL Lacertae-type object
              RG         Radio Galaxy
A question mark indicates an uncertain classification. Full details of the criteria used to categorize objects are given in the source paper of Perlman et al. (1998).

Redshift
The redshift of the object.

Other_Cat
A note indicating that the object is listed in another catalogs: 

             1     RASS Bright Source Catalog (RASSBSC: Voges et al.)
             2     Homogeneous Bright QSO Survey (HBQS: La Franca and Cristiani,
                   1997, AJ, 113, 1517 & 1998, AJ, 115, 1688)
             3     V Zwicky Catalog of Galaxies
             4     4C = 4th Cambridge Catalog
             5     Einstein IPC Slew Survey (Elvis et al. 1992, ApJS, 80, 257)
             6     FIRST Bright Quasar Survey (FBQS: Gregg et al. 1996,
                   AJ, 112, 407)
             7     B3 = 3rd Bologna Survey
             8     Las Campanas Redshift Survey (LCRS: Shectman et al. 1996,
                   ApJ, 470, 172)

Class
The HEASARC browse classification, based on the value of the object_type parameter

Contact Person

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

A service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysics Observatory (SAO)

Page Author: Browse Software Development Team
Last Modified: 8-Nov-2004