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RASSAEQSO - ROSAT All-Sky Survey/ASIAGO-ESO QSO Survey Catalog



This table contains some of the first results of a survey for bright quasars (V < 14.5 and R < 15.4) covering the northern hemisphere at Galactic latitudes |b| > 30 degrees. The photometric database is derived from the Guide Star and USNO catalogs. Quasars are identified on the basis of their X-ray emission measured in the ROSAT All-Sky Survey (RASS). The surface density of quasars brighter than 15.5 magnitudes turns out to be (10 +/- 2) x 10-3 degrees-2, about 3 times higher than that estimated by the Palomar-Green (PG) survey. In the paper, the quasar optical luminosity function (LF) at 0.04 < z <= 0.3 is computed and shown to be consistent with a luminosity-dependent luminosity evolution of the type derived by La Franca & Cristiani (1997AJ....113.1517L) in the range 0.3 < z <=2.2. The predictions of semianalytical models of hierarchical structure formation agree remarkably well with the present observations.

Catalog Bibcode



The Asiago-ESO/RASS QSO survey.
I. The catalog and the local QSO luminosity function.
    Grazian A., Cristiani S., D'Odorico V., Omizzolo A., Pizzella A.
   <Astron. J. 119, 2540 (2000)>


This table was created by the HEASARC in September 2010 based on the combination of the electronic versions of Tables 2, 3, and 4 from the reference paper which were obtained from the CDS (their catalog J/AJ/119/2540).


The authors defined three flux-limited samples, adopting the following photometric references:

(1) In the northern hemisphere, objects with 11.0 < V_GSC <= 14.5 in the GSC catalog.

(2) In the northern hemisphere, objects from the USNO catalog with 13.5 < R_USNO <= 15.4.

(3) In the southern hemisphere, the authors derived B_J magnitudes from the Digitized Sky Survey (DSS). These objects are not included in this table.

The authors cross-correlated the RASS catalog with the photometric databases described above for sources at Galactic latitudes |b| >= 30 deg, and with an RASS-BSC exposure time >= 300 s. Sources classified as extended in the RASS have been disregarded, while no selection based on optical morphology was applied. The looked for optical objects in the ranges 11.0 < V_GSC <= 14.5 and 13.5 < R_USNO <= 15.4 around the RASS sources, adopting a matching radius 3 times the rms positional uncertainty of each entry in the RASS catalog (typically 3 x 12"). In this way, very few (of the order of 0.1%) true identifications in the desired optical range were missed. The resulting catalog covers 8164 deg2 in the north and 5855 deg2 in the south. The list of the quasar candidates and the results of the spectroscopy are listed in this table. According to the authors, it should be noted that this table cannot be considered a list of optical identifications of X-ray sources. The cross-correlation procedure aims at finding optical objects in a desired magnitude range around X-ray sources. In some cases an entry may exist even if the true identification of the X-ray source is another (typically fainter) optical object. For example, even if the optical counterpart of the RASS source J013624.3+205712 is known to be the QSO 3C47.0, with V ~ 18.1 and z = 0.425, in this table the authors list an object with R_USNO = 14.7 that happens to fulfill the criteria of the cross-correlation.

HEASARC Implementation

The HEASARC has added a parameter called source_sample (q.v.) to allow users to easily identify from which sample (Table 2: USNO sources, Table 3: GSC sources, or Table 4: other spectroscopic identifications from a a set of additional candidates for which less restrictive selection criteria were used) a given source was taken.


The RASS X-ray source designation.

The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.1 seconds of time in the original table.

The Declination of the X-ray source in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.1 arcseconds in the original table.

The Galactic Longitude of the X-ray source.

The Galactic Latitude of the X-ray source.

The USNO R-band magnitude of the optical counterpart to the RASS source. This is available only for sources in the USNO sample.

The GSC V-band magnitude of the optical counterpart to the RASS source. This is available only for sources in the GSC sample.

The B_j-band magnitude of the optical counterpart to the RASS source, taken from the Digitized Sky Survey. This is available only for sources in the sample of other spectroscopic identifications.

The redshift of the optical counterpart to the RASS source.

This flag parameter is set to ':' to indicate that there is uncertainty in the identification and/or redshift.

The identification class of the source, where identifications as "BL Lac" or "Gal" have been taken from NED:

       AGN: emission-line object, irrespective of the line width
        BL: BL Lac object
       Gal: galaxy
      Star: star

This parameter was added by the HEASARC in order to allow users to easily identify from which of the 3 samples discussed in the reference paper a given source was taken. Sources which were in Table 2 (the USNO sample), Table 3 (the GSC sample), and Table 4 (other spectroscopic identifications) have been given source_sample values of 'USNO', 'GSC', and 'Other', respectively. 20 sources which were present in both the USNO and GSC samples have been given the source_sample value of 'USNO+GSC'.

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

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 27-Sep-2010