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1. CHAMP/SDSS Nearby Low-Luminosity AGN Catalog
ID:
ivo://nasa.heasarc/champsdssa
Title:
CHAMP/SDSS Nearby Low-Luminosity AGN Catalog
Short Name:
CHAMPSDSSA
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP; Green et al. 2004, ApJS, 150, 43) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relations between X-ray nuclear emission, nebular line emission, black hole masses, and the properties of the associated stellar populations. The authors provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). They present in their paper novel constraints that both X-ray luminosity L<sub>X</sub> and X-ray spectral energy distribution bring to the galaxy evolutionary sequence HII -> Seyfert/Transition Object -> LINER -> Passive suggested by optical data. In particular, the authors show that both L<sub>X</sub> and Gamma, the slope of the power law that best fits the 0.5 - 8 keV spectra, are consistent with a clear decline in the accretion power along the sequence, corresponding to a softening of their spectra. This implies that, at z ~ 0, or at low-luminosity active galactic nucleus (AGN) levels, there is an anticorrelation between Gamma and L/L<sub>Edd</sub>, opposite to the trend which is exhibited by high-z AGN (quasars). The turning point in the Gamma - L/L<sub>Edd</sub> LLAGN + quasars relation occurs near Gamma ~ 1.5 and L/L<sub>Edd</sub> ~ 0.01. Interestingly, this is identical to what stellar mass X-ray binaries exhibit, indicating that the authors have probably found the first empirical evidence for an intrinsic switch in the accretion mode, from advection-dominated flows to standard (disk/corona) accretion modes in supermassive black hole accretors, similar to what has been seen and proposed to happen in stellar mass black hole systems. The anticorrelation the authors find between Gamma and L/L<sub>Edd</sub> may instead indicate that stronger accretion correlates with greater absorption. Therefore, the trend for softer spectra toward more luminous, high-redshift, and strongly accreting (L/L<sub>Edd</sub> >~ 0.01) AGNs/quasars could simply be the result of strong selection biases reflected in the dearth of type 2 quasar detections. The cross-match of all ChaMP sky regions imaged by Chandra/ACIS with the SDSS DR4 spectroscopic footprint results in a parent sample of 15,955 galaxies on or near a chip and a subset of 199 sources that are X-ray detected. Among those, only 107 sources have an off-axis angle (OAA) Theta <0.2 degrees and avoid ccd=8 due to high serial readout noise; these 107 objects comprise the main sample that the authors employ for this study and that are listed in this table. The authors performed direct spectral fits to the X-ray counts distribution using the full instrument calibration, known redshift, and Galactic 21-cm column nH<sub>Gal</sub>. Source spectra were extracted from circular regions with radii corresponding to energy encircled fractions of ~90%, while the background region encompasses a 20 arcsec annulus, centered on the source, with separation 4 arcsecs, from the source region. Any nearby sources were excised, from both the source and the background regions. The spectral fitting was done via yaxx ('Yet Another X-ray eXtractor': Aldcroft 2006, BAAS, 38, 376), an automated script that employs the CIAO Sherpa tool. Each spectrum was fitted in the range 0.5 - 8 keV by two different models: (1) a single power law plus absorption fixed at the Galactic 21-cm value (model 'PL'), and (2) a fixed power law of photon index Gamma = 1.9 plus intrinsic absorption of column nH (model 'PLfix'). For the nine objects with more than 200 counts, the authors employed a third model in which both the slope of the power law and the intrinsic absorption were free to vary (model 'PL_abs'). This table was created by the HEASARC in January 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/705/1336/">CDS Catalog J/ApJ/705/1336/</a> file table1.dat. This is a service provided by NASA HEASARC .
2. GALEX/SDSS Quasar Catalog
ID:
ivo://nasa.heasarc/glxsdssqso
Title:
GALEX/SDSS Quasar Catalog
Short Name:
GLXSDSSQSO
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the result of an analysis of the broad-band UV and optical properties of z ~< 3.4 quasars matched in the Galaxy Evolution Explorer (GALEX) General Data Release 1 (GR1) and the Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3). Of the 6371 SDSS DR3 quasars covered by 204 GALEX GR1 tiles and listed in this table, 5380 (84%) have near-UV detections, while 3034 (48%) have both near-UV and far-UV detections using a matching radius of 7 arcseconds. Most of the DR3 sample quasars are detected in the near-UV until z ~ 1.7, with the near-UV detection fraction dropping to ~50% by z ~ 2. Statistical tests performed on the distributions of non-detections indicate that the optically selected quasars missed in the UV tend to be optically faint or at high redshift. The GALEX positions are shown to be consistent with the SDSS astrometry to within an rms scatter of 0.6 - 0.7 arcsecs in each coordinate, and the empirically determined photometric errors from multi-epoch GALEX observations significantly exceed the Poissonian errors quoted in the GR1 object catalogs. The UV-detected quasars are well separated from stars in UV-optical color-color space, with the UV-optical relative colors suggesting a marginally detected population of reddened objects due to absorption along the line of sight or dust associated with the quasar. The resulting spectral energy distributions (SEDs) cover ~350 - 9000 Angstroms (rest frame), where the overall median SED peaks near the Lyman-Alpha emission line, as found in other UV quasar studies. The large sample size allows the authors to construct median SEDs in small bins of redshift and luminosity, and they find that the median SED becomes harder (bluer) at UV wavelengths for quasars with lower continuum luminosity. The detected UV-optical flux as a function of redshift is qualitatively consistent with attenuation by intervening Lyman-absorbing clouds. This table was created by the HEASARC in October 2009 based on the electronic version of Table 2 from the reference paper which was obtained from the CDS (their catalog J/AJ/133/1780 file table2.dat). This is a service provided by NASA HEASARC .
3. GALEX/SDSS z=0.5-1.5 QSO Candidates Catalog
ID:
ivo://nasa.heasarc/glxsdssqs2
Title:
GALEX/SDSS z=0.5-1.5 QSO Candidates Catalog
Short Name:
GLXSDSSQS2
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
A sample of ~60,000 objects from the combined Sloan Digital Sky Survey-Galaxy Evolution Explorer (SDSS-GALEX) database with UV-optical colors that should isolate QSOs in the redshift range 0.5 to 1.5 is discussed. The authors use SDSS spectra of a subsample of ~ 4,500 to remove stellar and galaxy contaminants in the sample to a very high level, based on the 7-band photometry. In their paper, they discuss the distributions of redshift, luminosity, and reddening of the 19,100 QSOs (~96%) that they estimate to be present in their final sample of 19,812 point sources. This latter catalog is available in the present table. This paper is based on archival data from the Galaxy Evolution Explorer (GALEX) which is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034, and on data from the SDSS. This table was created by the HEASARC in March 2011 based on the electronic version of Table 2 from the reference paper which was obtained from the AJ web site. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
4. ROSAT All-Sky Survey and SDSS DR5 Sample of X-Ray Emitting AGN
ID:
ivo://nasa.heasarc/rassdssagn
Title:
ROSAT All-Sky Survey and SDSS DR5 Sample of X-Ray Emitting AGN
Short Name:
RASS/SDSSAGN
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains further results of a program aimed at yielding ~ 10<sup>4</sup> fully characterized optical identifications of ROSAT X-ray sources. The program employs X-ray data from the ROSAT All Sky Survey (RASS) and both optical imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS). RASS/SDSS data from 5740 deg<sup>2</sup> of sky spectroscopically covered in SDSS Data Release 5 (DR5) provide an expanded catalog of 7000 confirmed quasars and other active galactic nuclei (AGN) that are probable RASS identifications. Again, in this expanded catalog the identifications as X-ray sources are statistically secure, with only a few percent of the SDSS AGNs likely to be randomly superposed on unrelated RASS X-ray sources. Most identifications continue to be quasars and Seyfert 1 galaxies with 15 < m < 21 and 0.01 < z < 4, but the total sample size has grown to include very substantial numbers of even quite rare AGN, e.g., it now includes several hundreds of candidate X-ray-emitting BL Lac objects and narrow-line Seyfert 1 galaxies. In addition to exploring rare subpopulations, such a large total sample may be useful when considering correlations between the X-ray and the optical and may also serve as a resource list from which to select the ``best'' object (e.g., the X-ray-brightest AGN of a certain subclass at a preferred redshift or luminosity) for follow-up X-ray spectral or alternate detailed studies. 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 February 2007 based on the combination of the electronic versions of tables 1 through 6 from the above reference which were obtained from the electronic AJ website. It replaces a previous version containing the results presented by Anderson et al. (2003, AJ, 126, 2209) which were based on a cross-correlation of the RASS with optical data from very early on in the SDSS program, e.g., extending back to the 'Early Data Release' before SDSS photometric calibrations were complete. This is a service provided by NASA HEASARC .
5. ROSAT All-Sky Survey and SDSS Sample of X-Ray Emitting Stars
ID:
ivo://nasa.heasarc/rassdsstar
Title:
ROSAT All-Sky Survey and SDSS Sample of X-Ray Emitting Stars
Short Name:
RASSDSSTAR
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. Combining the RASS Bright and Faint Source Catalogs yields an average of about three X-ray sources per square degree. However, while X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient to determine the nature of an X-ray source. As a result, large-scale follow-up programs are required to construct samples of known X-ray emitters. The authors use optical data produced by the Sloan Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters cataloged in the RASS and falling within the SDSS Data Release 1 footprint. Most of these are bright stars with coronal X-ray emission unsuitable for SDSS spectroscopy, which is designed for fainter objects (g > 15<sup>mag</sup>). Instead, the authors use SDSS photometry, correlations with the Two Micron All Sky Survey (2MASS) and other catalogs, and spectroscopy from the Apache Point Observatory 3.5 m telescope to identify these stellar X-ray counterparts. Their sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest X-ray-selected samples of such stars. The authors derive distances to these stars using photometric parallax relations appropriate for dwarfs on the main sequence, and use these distances to calculate their X-ray luminosities L<sub>X</sub>. They also identify a previously unknown cataclysmic variable (CV) as a RASS counterpart. 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 the machine-readable version of Table 4 from the reference paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
6. SDSS NBCKDE Catalog of Photometrically Selected Quasar Candidates
ID:
ivo://nasa.heasarc/sdssnbckde
Title:
SDSS NBCKDE Catalog of Photometrically Selected Quasar Candidates
Short Name:
SDSSNBCKDE
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains a catalog of 1,015,082 quasar candidates selected from the photometric imaging data of the Sloan Digital Sky Survey (SDSS) using a non-parametric Bayesian classification kernel density estimator (NBC-KDE). It excludes 157,075 initial candidates that were culled as known or likely contaminants. The objects are all point sources to a limiting magnitude of i = 21.3 from 8417 deg<sup>2</sup> of imaging from SDSS Data Release 6 (DR6). This sample extends the previous catalog (Paper I: Richards et al. 2004, ApJS, 155, 257) by using the latest SDSS public release data and probing both ultraviolet (UV)-excess and high-redshift quasars. While the addition of high-redshift candidates reduces the overall efficiency (quasars:quasar candidates) of the catalog to ~80%, it is expected to contain no fewer than 850,000 bona fide quasars, which is ~8 times the number of the previous sample and ~10 times the size of the largest spectroscopic quasar catalog. Cross-matching between this photometric catalog and spectroscopic quasar catalogs from both the SDSS and 2dF survey yields 88,879 spectroscopically confirmed quasars. For judicious selection of the most robust UV-excess sources (~500,000 objects in all), the efficiency is nearly 97 - more than sufficient for detailed statistical analyses. The catalog's completeness to type 1 (broad-line) quasars is expected to be no worse than 70%, with most missing objects occurring at z < 0.7 and 2.5 < z < 3.0. In addition to classification information, the authors provide photometric redshift estimates (typically good to Delta(z) +/- 0.3 [2-sigma]) and cross-matching with radio, X-ray, and proper-motion catalogs. Finally, the authors have considered the catalog's utility for determining the optical luminosity function of quasars and are able to confirm the flattening of the bright-end slope of the quasar luminosity function at z ~ 4 as compared to z ~ 2. 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 based on an electronic version of Table 1 in the reference paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
7. Sloan Digital Sky Survey Broad Absorption Line Quasars Catalog: 3rd Data Release
ID:
ivo://nasa.heasarc/sdssbalqso
Title:
Sloan Digital Sky Survey Broad Absorption Line Quasars Catalog: 3rd Data Release
Short Name:
SDSSBALQSO
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
The Sloan Digital Sky Survey (SDSS) Broad Absorption Line (BAL) Quasars Catalog (based on the 3rd SDSS Data Release) contains a total of 4784 unique BAL quasars from the SDSS DR3 (<a href="https://cdsarc.cds.unistra.fr/ftp/cats/VII/243">CDS Cat. <VII/243></a>). An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000 km/s in the C IV and Mg II absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift z, with the power-law spectral index and amount of dust reddening as additional free parameters. The authors characterize their sample through the traditional 'balnicity' index BI and a revised absorption index AI, as well as through parameters such as the width, outflow velocity, fractional depth, and number of troughs. From a sample of 16,883 quasars at 1.7 <= z <= 4.38, they identify 4386 (26.0%) quasars with broad C IV absorption, of which 1756 (10.4%) satisfy traditional selection criteria. From a sample of 34,973 quasars at 0.5 <= z <= 2.15, they identify 457 (1.31%) quasars with broad Mg II absorption, 191 (0.55%) of which satisfy traditional selection criteria. They find that BAL quasars may have broader emission lines on average than other quasars. 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 July 2008 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/165/1">CDS catalog J/ApJS/165/1</a> file table4.dat. This is a service provided by NASA HEASARC .
8. Sloan Digital Sky Survey DR6 Galaxy Clusters Catalog
ID:
ivo://nasa.heasarc/sdsswhlgc
Title:
Sloan Digital Sky Survey DR6 Galaxy Clusters Catalog
Short Name:
SDSSWHLGC
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
Clusters of galaxies in most of the previous catalogs have redshifts z <= 0.3. Using the photometric redshifts of galaxies from the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), the authors identify 39,716 clusters in the redshift range 0.05 < z < 0.6 with more than eight luminous (M_r <= -21) member galaxies. Cluster redshifts are estimated accurately with an uncertainty of less than 0.022. The contamination rate of member galaxies is found to be roughly 20%, and the completeness of member galaxy detection reaches ~90%. Monte Carlo simulations show that the cluster detection rate is more than 90% for massive (M_200 > 2 x 10<sup>14</sup> M_sun, where M_200 is the total mass within the radius in which the mean mass density is 200 times the critical cosmic mass density) clusters of z <= 0.42. The false detection rate is ~5%. The authors obtain the richness, the summed luminosity, and the gross galaxy number within the determined radius for identified clusters. They are tightly related to the X-ray luminosity and temperature of the clusters. Cluster mass is related to the richness and summed luminosity with M_200 ~ R<sup>(1.90+/-0.04)</sup> and M_200 ~ L_r<sup>(1.64+/-0.03)</sup>, respectively. In addition, 790 new candidate X-ray clusters are found by cross-identification of these clusters with the source list of the ROSAT X-ray All-Sky Survey. This table was created by the HEASARC in August 2009 based on electronic versions of Tables 1 and 2 from the paper which were obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .
9. Sloan Digital Sky Survey DR10 New White Dwarf Catalog
ID:
ivo://nasa.heasarc/sdssdr10wd
Title:
Sloan Digital Sky Survey DR10 New White Dwarf Catalog
Short Name:
SDSSDR10WD
Date:
09 May 2025
Publisher:
NASA/GSFC HEASARC
Description:
The authors report the discovery of 9,088 new spectroscopically confirmed white dwarfs and subdwarfs in the Sloan Digital Sky Survey (SDSS) Data Release 10 (DR10). They obtain T<sub>eff</sub>, log g and masses for hydrogen-atmosphere white dwarf stars (DAs) and helium-atmosphere white dwarf stars (DBs), and estimate the calcium/helium abundances for the white dwarf stars with metallic lines (DZs) and carbon/helium for carbon-dominated spectra (DQs). They found 1 central star of a planetary nebula, 2 new oxygen spectra on helium-atmosphere white dwarfs, 71 DQs, 42 hot DO/PG1159s, 171 white dwarf+main-sequence star binaries, 206 magnetic DAHs, 327 continuum-dominated DCs, 397 metal-polluted white dwarfs, 450 helium-dominated white dwarfs, 647 subdwarfs and 6887 new hydrogen-dominated white dwarf stars. The targeted white dwarfs were required to be point sources with clean photometry, and to have USNO-B Catalog counterparts (Monet et al.. 2003, AJ, 125, 984, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/I/284">CDS Cat. I/284</a>). They were also restricted to regions inside the DR7 imaging footprint and required to have colors within the ranges g < 19.2, (u-r) < 0.4, -1 < (u-g) < 0.3, -1 < (g-r) < 0.5 and to have low Galactic extinction A<sub>r</sub> < 0.5 mag. Additionally, targets that did not have (u-r) < -0.1 and (g-r) < -0.1 were required to have USNO proper motions larger than 2 arcseconds per century (20 milliarcseconds per year). Objects satisfying the selection criteria that had not been observed previously by the SDSS were denoted by the WHITEDWARF_NEW target flag, while those with prior SDSS spectra are assigned the WHITEDWARF_SDSS flag. Some of the latter were re-observed with BOSS in order to obtain the extended wavelength coverage that the BOSS spectrograph offers. The color selection used includes DA stars with temperatures above ~14,000 K, helium-atmosphere white dwarfs above ~8000 K, as well as many rarer classes of white dwarfs. Hot subdwarfs (sdB and sdO) were targeted as well. Note that this catalog does not include stars from the earlier SDSS white dwarf catalogs, e.g., Eisenstein et al. (2006, ApJS, 167, 40, available in the HEASARC database as the SDSSDWDSD table), Kleinman et al. (2013, ApJS, 205, 5, available in the HEASARC database as the SDSSDR7WD table).. This table was created by the HEASARC in October 2017 based on an electronic version of Table 6 from the reference paper which was obtained from the CDS as their catalog J/MNRAS/446/4078 file table6.dat. This is a service provided by NASA HEASARC .

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