- ID:
- ivo://nasa.heasarc/sdssquasar
- Title:
- Sloan Digital Sky Survey Quasar Catalog (Twelfth Data Release: DR12Q)
- Short Name:
- SDSS(QSO)
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Data Release 12 Quasar Catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III (SDSS-III). This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities M_i_[z=2] < -20.5 (in a LambdaCDM cosmology with H<sub>0</sub> = 70 km/s/Mpc, Omega<sub>M</sub> = 0.3, and Omega<sub>Lambda</sub> = 0.7), and either display at least one emission line with a full width at half maximum (FWHM) larger than 500 km/s or, if not, have interesting/complex absorption features. The catalog also includes previously known quasars (mostly from SDSS-I and II) that were re-observed by BOSS. The catalog contains 297,301 quasars (272,026 are new discoveries since the beginning of SDSS-III) detected over 9376 deg<sup>2</sup> with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with z > 2.15 (184,101, of which 167,742 are new discoveries) is about an order of magnitude greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C IV, C III], Mg II). The catalog identifies 29,580 broad absorption line quasars and their characteristics are listed in the file dr12qbal.dat that is available at the CDS (<a href="http://cdsarc.u-strasbg.fr/ftp/cats/VII/279/">http://cdsarc.u-strasbg.fr/ftp/cats/VII/279/</a>). For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and Palomar Transient Factory multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3600-10,500 Angstrom at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Catalog Archive Server at <a href="http://www.sdss.org/dr12/data_access/">http://www.sdss.org/dr12/data_access/</a>. In their paper, the authors also provide a supplemental list of an additional 4,841 quasars that have been identified serendipitously outside of the superset defined to derive the main quasar catalog, available as the file dr12qsp.dat that is available at the CDS (<a href="http://cdsarc.u-strasbg.fr/ftp/cats/VII/279/">http://cdsarc.u-strasbg.fr/ftp/cats/VII/279/</a>). This table contains the final quasar catalog of the SDSS-III/BOSS survey resulting from five years of observations. The catalog, which the authors call "DR12Q", contains 297,301 quasars, 184,101 of which have z > 2.15. the authors provide robust identification from visual inspection and refined redshift measurements based on the result of a principal component analysis of the spectra. The present catalog contains about 80% more quasars than their previous release (Paris et al., 2014, "DR10Q", <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VII/270">CDS Cat. VII/270</a>). In SDSS-III, all fluxes in the 5 SDSS bands (u, g, r, i and z) are expressed in terms of "nanomaggies" (nMgy), which are a convenient linear unit. These quantities are related to standard AB magnitudes thus: an object with a flux F given in nMgy has a Pogson magnitude (on the AB scale) m = [22.5 mag] - 2.5*log<sub>10</sub>(F). A flux of 1 Mgy is therefore close to 3631 Jy, and 1 nMgy = ~3.631 uJy (µJy). This table was updated to DR12Q in July 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/VII/279">CDS Catalog VII/279</a> file dr12q.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/sdsscxoqso
- Title:
- Sloan Digital Sky Survey Quasars Detected by Chandra
- Short Name:
- SDSSCXOQSO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- 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 10<sup>22</sup> cm<sup>-2</sup>, 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 <a href="http://www.sdss.org/">http://www.sdss.org/</a>. 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. This is a service provided by NASA HEASARC .
