Browse
this table...

DXRBS - ROSAT Deep X-Ray Radio Blazar Survey Catalog

HEASARC
Archive

Overview

The authors 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, restricting their candidate list to serendipitous flat radio spectrum sources (Alphar <= 0.70, where SNu ~ Nu-Alphar). In their first paper (DXRBS-I), the authors discuss their survey methods, identification procedure, and first results. Their survey was 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. The identifications presented therein showed that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (LX, LR) parameter space within which large fractions of the blazar population lie. Particularly important was the identification of a large population of FSRQs (>=25% of DXRBS-I FSRQs) with ratios of X-ray to radio luminosity >= 10-6 (Alpharx <= 0.78). In addition, as a result of their greater sensitivity, the DXRBS-I already more than doubled the number of FSRQs in complete samples with 5-GHz (radio) luminosities between 1031.5 and 1033.5 ergs/s/Hz, and filled in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS-I was 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.

In DXRBS-II, the authors presented new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with the DXRBS-I objects and already-known sources, their sample now contained 298 identified objects: 234 radio-loud quasars [181 flat-spectrum quasars: FSRQ (Alphar <= 0.50) and 53 steep-spectrum quasars: SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus, the selection technique was ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes of ~ 50 mJy and 0.1 - 2.0 keV X-ray fluxes of a few times 10-14 erg/cm2/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification.

The DXRBS-I entries in this catalog (identified by having values of the parameter dxrbs_part equal to 1) contain data for 85 identified sources meeting the authors' selection criteria. A number of sources were serendipitously observed by ROSAT on more than one occasion, and, for completeness, the WGACAT positions and values for these multiply observed sources are listed separately, resulting in 102 DXRBS-I 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).

The DXRBS-II entries in this catalog (identified by having values of the parameter dxrbs_part equal to 2) contain data for 106 identified sources meeting the authors' selection criteria. A number of sources were serendipitously observed by ROSAT on more than one occasion, and, for completeness, the WGACAT positions and values for these multiply observed sources are listed separately. In one case (1WGA J0513.8+0156') the source was detected twice by ROSAT and there are two possible optical counterparts: there are 2 entries for each X-ray observation corresponding to the different conterparts, resulting in a total of 4 entries for this source. There are 92 DXRBS-II sources with 1 X-ray observation, 11 sources with 2 X-ray observations, 2 sources with 4 X-ray observations and 1 source with 5 X-ray observations) resulting in 127 DXRBS-II entries for 106 sources in this catalog. Four of the DXRBS-I objects (1WGA J0421.5+1433, 1WGA J0528.5-5820, 1WGA J1057.6-7724 and 1WGA J1222.6+2934) were also included in DXRBS-II as higher signal-to-noise ratio (S/N) spectra were available. Thus, in the sum of the 2 DXRBS parts presented here, there are 229 entries corresponding to 191 newly discovered sources. The 109 previously identified blazars, 97 of which were listed in Table 6 of DXRBS-I, are not included in this table.


Catalog Bibcodes

1998AJ....115.1253P
2001MNRAS.323..757L

References

The Deep X-ray Radio Blazar Survey. I. Methods and first results.
    Perlman E.S., Padovani P., Giommi P., Sambruna R., Jones L.R.,
    Tzioumis A., Reynolds J.
   <Astron. J. 115, 1253 (1998)>
   =1998AJ....115.1253P
The Deep X-Ray Radio Blazar Survey (DXRBS) - II. New identifications.
    Landt H., Padovani P., Perlman E.S., Giommi P., Bignall H., Tzioumis A.
   <Mon. Not. R. Astron. Soc. 323, 757 (2001)>
   =2001MNRAS.323..757L

Provenance

This table was created by the HEASARC in March 2012 based on the merger of files table3.dat and table4.dat from the CDS Catalog J/AJ/115/1253 (DXRBS-I) and files table4.dat and table5.dat from the CDS Catalog J/MNRAS/323/757 (DXRBS-II). (Note that it does not include the list of 97 previously identified blazars given in table6.dat of the CDS Catalog J/AJ/115/1253.) The current DXRBS table replaced a previous version (ingested in March 1999) which included only the DXRBS-I tables 3 and 4.

Parameters

Dxrbs_Part
This parameter created by the HEASARC identifies from which part of the DXRBS the entry comes: a value of 1 indicates entries from DXRBS-I, 2 entries from DXRBS-II.

Entry_Number
This parameter created by the HEASARC uniquely identifies sources within a given DXRBS part (I or II), and is a sequence number in order of increasing J2000 RA. Thus, the two parameters dxrbs_part and entry_number uniquely specify a DXRBS source.

Name
The name of the object, using the standard IAU nomenclature scheme with the prefix of '1WGA' for 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. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 0.1 seconds of time.

Dec
The Declination of the X-ray source in the WGACAT database, in the selected equinox. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 1 arcsecond.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The off-axis angle of the X-ray source from the center of the PSPC field of view, in arcminutes.

RA_Radio
The Right Ascension of the radio counterpart to the WGACAT X-ray source in the selected equinox, in either the PMN or the GB6 Catalogs. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 0.1 seconds of time.

Dec_Radio
The Declination of the radio counterpart to the WGACAT X-ray source in the selected equinox, in either the PMN or the GB6 Catalogs. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 1 arcsecond.

RA_Optical
The Right Ascension of the optical counterpart to the WGACAT X-ray source in the selected equinox. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 0.1 seconds of time.

Dec_Optical
The Declination of the optical counterpart to the WGACAT X-ray source in the selected equinox. The co-ordinates in the original input table were J2000 equatorial coordinates and were given to a precision of 1 arcsecond.

Position_Flag
This flag parameter is set to 'n' if there is a note concerning the position of the source in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

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

Xray_Opt_Offset_Error
The rms uncertainty in the offset between the X-ray and the optical positions, in arcseconds, given only for DXRBS-II sources.

Select_Flag
This flag parameter is set to 'N' to indicate that the source does not meet the strict DXRBS selection criteria, given only for DXRBS-II sources.

Source_Flag
This flag parameter is set to 'n' if there is a note concerning the individual source in Section 3.4 of the DXRBS-II paper, also available in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

Count_Rate
The WGACAT ROSAT PSPC count rate of the source, in ct s-1. For objects observed more than once by ROSAT, the count rate, hardness ratios and X-ray flux are given for each observation.

Hardness_Ratio
The WGACAT ROSAT PSPC hardness ratio of the source, being the ratio between the hard (0.87 - 2.0 keV) and medium (0.4 - 0.86 keV) band count rates. (See Padovani and Giommi (1996, MNRAS, 279, 526). For objects observed more than once by ROSAT, the count rate, hardness ratios and X-ray flux are given for each observation. It is available only for DXRBS-II sources.

Fx
The 0.1 - 2 keV X-ray flux of the source, in erg s-1 cm-2, not corrected for Galactic extinction, and 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. For objects observed more than once by ROSAT, the count rate, hardness ratios and X-ray flux are given for each observation.

Fx_Dens_1keV
The unabsorbed flux density of the source at 1 keV, in microJansky, 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_Flux_6_cm
The logarithm of the ratio between the 0.3 - 3.5 keV X-ray flux and the radio flux at 6 cm of the source, in erg s-1 cm-2 Jy-1.

Flux_6_cm
The radio flux of the source at 6 cm, in mJy.

Spectral_Index
The radio spectral index of the source, calculated as described in Section 2.1 of DXRBS-I and/or Section 2.2 of DXRBS-II.

Spectral_Index_Flag
This flag parameter is set to 'n' if there is a note concerning the radio spectral index of the source in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

BJ_Mag
The Bj (blue) magnitude of the optical counterpart (from COSMOS). It is available only for DXRBS-II sources.

BJ_Mag_Flag
This flag parameter is set to 'n' if there is a note concerning the Bj magnitude of the source in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

Omag_Limit
This parameter is set to '>' if only an upper limit is available for the corresponding parameter value.

Omag
The O-plate (blue) magnitude of the optical counterpart (from APM, except if the corresponding flag parameter is set to 'n' in which case see the cooresponding note for the source). It is available only for DXRBS-II sources.

Omag_Flag
This flag parameter is set to 'n' if there is a note concerning the O magnitude of the source in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

Emag_Limit
This parameter is set to '>' if only an upper limit is available for the corresponding parameter value.

Emag
The E-plate (red) magnitude of the optical counterpart (from APM, except if the corresponding flag parameter is set to 'n' in which case see the cooresponding note for the source). It is available only for DXRBS-II sources.

Emag_Flag
This flag parameter is set to 'n' if there is a note concerning the E magnitude of the source in the file http://cdsarc.u-strasbg.fr/ftp/cats/J_MNRAS/323/757/notes.dat. It is thus applicable only for DXRBS-II sources.

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

    BL Lac     BL Lacertae-type object (a sub-class of blazars)
    FSRQ       Flat-Spectrum Radio-Loud Quasar (a sub-class of blazars)
    NLRG       Narrow-Line Radio Galaxy
    RG         Radio Galaxy
    SSRQ       Steep-Spectrum Radio Quasar
  
A question mark indicates an uncertain classification. Full details of the criteria used to categorize objects are given in the DXRBS-I and -II source papers.

Redshift
The redshift of the source. This was computed, whenever possible, by taking the mean of the values derived from the narrow lines. Where only a single (broad) emission line was observed, it was assumed to be Mg II 2798 Angstroms. When only weak features were observed, the redshift is marked as questionable (redshift_flag = '?') and (for DXRBS-II sources) the object is discussed individually in Section 3.4 of the DXRBS-II source paper.

Redshift_Error
The sample standrad deviation in the redshift. No error in the redshift is given if only 1 emission line was present in the optical spectrum. This parameter is available only for DXRBS-II sources.

Redshift_Flag
This flag parameter is set to '?' to indicate that the redshift is unknown (for DXRBS-I sources) or uncertain (for DXRBS-II sources, as discussed above in the description of the redshift parameter).

Error_Radius
The error radius of the WGACAT X-ray source position, in arcseconds. This parameter is explicitly given only for DXRBS-I sources. For DXRBS-II sources, it can be estimated using the value of the off-axis angle for the source (the off_axis parameter) using the criteria given in Table 3 of the DXRBS-II reference paper, and repeated here:


  off_axis offset         error_radius
    (arcminutes)           (arcseconds)

    0 - 10                 13.0
   10 - 20                 18.1
   20 - 30                 28.6
   30 - 40                 36.1
   40 - 50                 42.0
   50 - 60                 53.4
  

Ref_Position
The primary survey/catalog reference source for the accurate positioning (identification) of the DXRBS-I source, 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)
  

Optical_Error_Radius
The uncertainty in the optical counterpart position (given only for DXRBS-I sources), in arcseconds.

Xray_Opt_Offset_Sigma
The ratio of the X-ray source to optical counterpart positional offset to its uncertainty (xray_opt_offset/xray_opt_offset_error), i.e., the number of sigma by which the positions disagree.

Bmag_Limit
This parameter is set to '>' if only an upper limit is available for the corresponding parameter value.

Bmag
The B-magnitude of the optical counterpart to the DXRBS-I source, obtained as discussed in Section 4 of DXRBS-I.

Rmag_Limit
This parameter is set to '>' if only an upper limit is available for the corresponding parameter value.

Rmag
The R-magnitude of the optical counterpart to the DXRBS-I source, obtained as discussed in Section 4 of DXRBS-I.

Other_Catalogs
This parameter contains coded references to other catalogs in which the source is listed, as follows:

         1: RASS Bright Source Catalog, CDS Cat. <IX/10>
         2: HBQS, Homogeneous Bright QSO Survey, CDS Cat. <J/A+AS/112/347>
         3: V Zwicky Catalog of Galaxies, CDS Cat. <VII/190>
         4: 4C, Fourth Cambridge Survey, CDS Cat. <VIII/4>
         5: Einstein Slew Survey, Elvis et al., 1992ApJS...80..257E
         6: FIRST Bright Quasar Survey, See CDS Cat. <VIII/51>
         7: B3, Third Bologna Survey, CDS Cat. <VIII/37>
         8: Las Campanas Redshift Survey, CDS Cat. <VII/203>
  

Class
The HEASARC Browse object 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.

Page Author: Browse Software Development Team
Last Modified: 2-Apr-2012