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SDSSCXOQSO - Sloan Digital Sky Survey Quasars Detected by Chandra

HEASARC
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Overview

The authors have studied the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project (ChaMP). Their highest-confidence matched sample (which this HEASARC table comprises) includes 1135 X-ray detected quasars in the redshift range 0.2 < z < 5.4, representing some 36 Msec of effective exposure. In their paper, the authors provide catalogs of QSO properties, and describe their novel method of calculating X-ray flux upper limits and effective sky coverage. Spectroscopic redshifts are available for about 1/3 of the detected sample; elsewhere, redshifts are estimated photometrically. The authors have detected 56 QSOs with redshift z > 3, substantially expanding the known sample. They find no evidence for evolution out to z ~ 5 for either the X-ray photon index Gamma or for the ratio of optical/UV to X-ray flux Alpha_ox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022 cm-2, but the fraction might reach ~1/3 if most nondetections are absorbed. The authors confirm a significant correlation between Alpha_ox and optical luminosity, but it flattens or disappears for fainter (M_B >~ -23) active galactic nucleus (AGN) alone. They report significant hardening of Gamma both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and their findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, they find no evidence for unusual distributions of either Alpha_ox or Gamma.

Much more information on the SDSS is available at the project's web site at http://www.sdss.org/.


Catalog Bibcode

2009ApJ...690..644G

References

A Full Year's Chandra Exposure on Sloan Digital Sky Survey Quasars from the
Chandra Multiwavelength Project
    Green P.J., Aldcroft T.L., Richards G.T., Barkhouse W.A., Constantin A.,
    Haggard D., Karovska M., Kim D.-W., Kim M., Vikhlinin A., Anderson S.F.,
    Mossman A., Kashyap V., Myers A.C., Silverman J.D., Wilkes B.J.,
    Tananbaum H.
    <Astrophys. J. 690, 644 (2009)>
    =2009ApJ...690..644G

Provenance

This table was created by the HEASARC in April 2009 based on the machine-readable version of Table 2 ('Properties of SDSS Quasars Detected by Chandra') which was obtained from the ApJ website.

Parameters

SDSS_ObsID
The SDSS object identifier.

RA
The Right Ascension of the SDSS object in the selected equinox. This was given in J2000.0 equatorial decimal degree coordinates to a precision of 10 microdegree (0.036") in the original reference.

Dec
The Declination of the SDSS object in the selected equinox. This was given in J2000.0 equatorial decimal degree coordinates to a precision of 1 microdegree (0.0036") in the original reference.

LII
The Galactic Longitude of the SDSS object.

BII
The Galactic Latitude of the SDSS object.

Imag
The SDSS asinh i-band PSF magnitude of the object (dereddened).

Phot_Redshift
The photometric redshift of the object: see Weinstein et al. (2004, ApJS, 155, 243).

Phot_Redshift_Prob
The photometric redshift range probability.

Phot_Redshift_Lower
The photometric redshift lower limit.

Phot_Redshift_Upper
The photometric redshift upper limit.

Redshift
The best redshift of the object: the value quoted is spectroscopic if the value is different from the value of phot_redshift.

Ref_Redshift
A reference code for the source of the spectroscopic redshift: 'S' if from the SDSS Data Release 6 (DR6), 'O' if from ChaMP, and 'R' if a published reference from NED.

Name
The standard ChaMP X-ray source designation, using the 'CXOMP J' prefix for Chandra X-Ray Observatory Multiwavelength Project X-ray sources and the truncated J2000.0 coordinates of the source, e.g., HHMMSS.s+DDMMSS.

Champ_Srcid
The ChaMP internal X-ray source name, in the format 'XSoooooBc_nnn', where oooo = Chandra obsid, c = ACIS CCD ID, and nnn = source number on that CCD.

Off_Axis
The Chandra off-axis angle of the X-ray counterpart to the SDSS object, in arcminutes.

Counts
The net Chandra counts of the X-ray counterpart to the SDSS object, in the 0.3 - 8 keV range.

Counts_Error
The RMS uncertainty in the net Chandra counts.

Exposure
The vignetting-corrected exposure time for the Chandra counterpart to the SDSS object, in seconds (s).

NH_Gal
The Galactic absorbing H I column density, in H atoms cm-2, in the direction of the SDSS object, from Dickey and Lockman (1990, ARAA, 28, 215).

NH
The best-fit intrinsic absorbing H I column density, in H atoms cm-2, inferred from fitting the X-ray spectrum (only given for sources with more than 200 X-ray counts).

NH_Pos_Err
The 90% upper error in the best-fit intrinsic absorbing H I column density, in H atoms cm-2.

NH_Neg_Err
The 90% lower error in the best-fit intrinsic absorbing H I column density, in H atoms cm-2.

Spect_Index
The best-fit power-law (photon energy) index, Gamma, to the Chandra X-ray spectrum. Gamma is the photon number index of an assumed power-law continuum EGamma.

Spect_Index_Pos_Err
The 90% upper error in the best-fit power-law (photon energy) index, Gamma, to the Chandra X-ray spectrum.

Spect_Index_Neg_Err
The 90% lower error in the best-fit power-law (photon energy) index, Gamma, to the Chandra X-ray spectrum.

Flux
The 0.5 - 8 keV flux of the Chandra counterpart to the SDSS object, in erg/cm2/s.

Log_2keV_Luminosity
The logarithm of the monochromatic 2-keV luminosity, L_2keV, of the Chandra counterpart to the SDSS object, in erg/s/Hz.

Log_2500a_Luminosity
The logarithm of the monochromatic 2500-Angstrom optical/UV luminosity, log L_2500A, of the Chandra counterpart to the SDSS object, in erg/s/Hz.

Opt_Xray_Spect_Index
The optical/UV to X-ray spectral index, Alpha_ox, of the Chandra counterpart to the SDSS object, defined as the slope of a hypothetical power law from 2500 Angstroms to 2 keV, i.e., 0.3838(log L_2500A - log L_2keV).

Flux_20_cm
The integrated 1.4-GHz (20-cm) flux density of the radio counterpart (FIRST or NVSS) to the SDSS object, in mJy.

Flux_20_cm_Flag
This flag parameter is set to 1 to indicate that there is multiple or extended radio morphology of the radio counterpart in FIRST. For such sources, either the lower spatial resolution NVSS flux densities or the summed FIRST flux densities are given.

Radio_Loudness
The radio loudness R of the radio counterpart to the SDSS object, defined as R = 0.4 [imag + 2.5 log(flux_20cm/3.631E06)]. A value of the 20-cm flux density of 1 mJy is assumed as an upper limit where there is no detected FIRST source.

Spectral_Class
The coded spectral classification of the SDSS object, if avaliable (0 implies no classification). Broad (BAL) and narrow (NAL) absorption lines were identified by visual inspection of the spectra. (A classification of Narrow-Line Seyfert 1 (NLS1) indicates that the spectral measurement of FWHM(Hbeta) gave a value less than 2000 km/s, notice). The non-zero values imply the following:

      1 = BAL
      2 = NAL
      3 = NLS1
  

Chandra_Target
This parameter contains a value of 1 if the object was the target of the Chandra observation, i.e., it is not serendipitous.

Comments
This parameter contains miscellaneous comments concerning the source.

Class
The HEASARC Browse object classification, based upon the value of the spectral_class parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 27-Apr-2009