MILLIQUAS - Million Quasars Catalog, Version 4.4 (6 February 2015)
This table contains the Million Quasars (MILLIQUAS) Catalog, Version 4.4 (6 February 2015). It is a compendium of all type-I QSOs and AGN, and BL Lac objects, complete from the literature, up to 25 January 2015. High-confidence (80+%) photometric SDSS and radio/X-ray associated objects are included, plus type-II objects, which bring the total number of objects to 1,151,011. Objects have been de-duplicated across catalogs, and the earliest name and best redshift are presented for each. Astrometry is fixed onto a combined APM/USNO-B/SDSS optical background, and is accurate to within 1-2 arcseconds in every case. Note that multiply-lensed images are listed as single objects.
This version has the following changes from the previous edition:
(1) Quasar data brought up to publications as at 25 January 2015. (2) Some reprocessing of the SDSS-DR12 and SDSS-DR12Q (www.sdss.org) data. About 1000 type-1 objects reclassified to type-2. (3) Photometric candidate likelihoods and redshifts have been recalibrated using the SDSS-DR12Q quasars as the benchmark.The contents are relatively simple, each object is shown as one entry with the sky coordinates, its name, red and blue optical magnitudes, PSF class, redshift, and the source catalog for its name and redshift, plus a radio and/or X-ray identifier where applicable.
The author's current plans are to keep this updated as a "living" QSO catalog, with a view to publishing a half-million confirmed quasars catalogue in 2015.
Questions/comments/praise/complaints may be directed to Eric Flesch at email@example.com. He requests that, if you use this catalog in published research, that you please add a small mention (acknowledgment).
This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
This research has also made use of data obtained from the Chandra Source Catalog, provided by the Chandra X-ray Center (CXC) as part of the Chandra Data Archive.
Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy. The SDSS-III web site is http://www.sdss3.org/.
0.1 22Apr09 0.3 6May09 Added a radio identifier and an X-ray identifier. 0.5 11May09 Added 30816 objects from newly calculated associations to XMM, Chandra and SUMSS detections, plus some tweaks. Also added QSO probability % for non-confirmed QSOs. 0.8 22Jun09 Added Chandra Source Catalog 1.0 (2009). 1.0 03Aug09 Extensive de-duplication. XMM Slew Catalog data added. 1.4 20Aug09 Misc fixes in the de-duplications. 1.5 29Aug09 Used XMM Slew Catalog v1.3 2.0 14Jun10 Used XMM Slew Catalog v1.4, XMM3, and XAssist4. 2.1 17Aug10 Removed 8627 NELGs masquerading as AGNe. 2.2 7Jan11 About 10,000 AGNe from the previous edition are now presented as QSOs. 796 AGNe mistakenly expunged in 2.1 have been restored. 2.3 5Mar11 SDSS DR-8 and BOSS targets have been included and the threshold for inclusions of candidates has been raised from 60% to 70%. 2.4 5Jun11 Improved QSO-likelihood calculation for the BOSS targets, so 17% of previously included BOSS targets drop out. Newly included data from several sources (see above). 2.5 20Jul11 Some de-duplication of quasars which were discovered prior to 1990, 200 recent NED quasars added, some radio/X-ray associations to USNO-B optical data added. 2.6 10Sep11 The USNO-B catalog has been added and hard-deduplicated against APM and SDSS data to make a background pool of 1.04 billion optical objects. Also, about 12 million orphaned one-color APM objects have been removed. There are consequently improvements in this catalog's optical selections and astrometry without changing the net totals much. XMM Slew 1.5 catalog added. Some further astrometric fixes and de-duplications of early quasars. 2.7 5Nov11 New quasar publications to 4 November 2011 were added, and a few fixes on individual objects incorporated. 2.8 29Jan12 Completed the fixes of non-astrometric relic data from the Veron-Cetty & Veron 13th edition. About 150 other fixes. Quasars compilation updated through 27 January 2012. 2.9 2Apr12 Data brought up to publications as of 31 March 2012, about 50 astrometric fixes done, and the new FIRST radio catalog, 12Feb16 version, incorporated. 2.10 6Aug12 Data brought up to publications as of 31 July 2012, including the SDSS-DR9 release, XAssist XMM-Newton and Chandra X-ray data updated to 30 June 2012; as this is a catalog for type I (broad-line) objects, 1870 Seyfert-2s, 532 LINERs, and 6 NELGs were removed, but BL Lacs were retained as unconstrained emission objects. 3.0 9Sep12 Data brought up to publications as of 31 August 2012. Redshifts are calculated for the XDQSO photometric quasar candidates. Fixed issues with 30 DEEP2 object. Separated out 15 SDSS-DR9 object that had been conflated with others. QSO-AGN separator restored to that used through v2.9, thus ~5000 QSOs were re-classified as AGNe. AGNe historic names sourced from the Principal Galaxy Catalogue. 3.1 22Oct12 Quasar data brought up to publications as of 20 Oct. 2012, including the new DR9 Quasar catalog (Paris I., 2012, arXiv:1210.5166). 3.2 10Feb13 Quasar data brought up to publications as of 9 Feb. 2013. MMT quasar positions fixed, and made a few small miscellaneous fixes. 3.3 7Apr13 Quasar data brought up to publications as at 6 April 2013. Added 713 new quasars from Palanque-Delabrouille et al. (2013, A&A, 551, A29). Included SWIRE data, consisting of 117 confirmed quasars and >20K photometric quasars from Rowan-Robinson et al. (2013, MNRAS, 428, 1958). Located 8 QSOs that were previously uncertainly located and removed 1 that had no credible candidates. Removed 26 SDSS-DR9 quasars after inspection showed they were only artifacts. Removed 144 questionable quasars from Iovino et al. (1996, A&AS, 119, 265). Removed 8 blazars classified as white dwarfs by the SDSS DR7 WD Cat (2013,ApJS,204,5). Miscellaneous: 4 moves, 2 de-dups, and 4 deletions found after extensive trawling. 3.4 11Jul13 Quasar data brought up to publications as at 11 July 2013. The author's paper (2013,PASA,30,4) marked 9 QSOs as uncertainly located. Of those: (a) Q 0112-27 is finally sited at J011517.2-271223, courtesy Cyril Hazard. (b) Q 0752+617 is moved to J075646.6+613639, r=16.9, b=17.4, as a better fit with its co-published quasar (NOTNI 16, r=16.7, b=17.2). Added 92 new quasars from Cyril Hazard. Q 1409+732 was found to be sited on a plate flaw, and is now moved one arcmin due East to perfect optical fit at J141003.2+725939, r=19.3, b>22. XAssist v4 XMM-Newton & Chandra X-ray data updated to 30-June-2013. 3.5 11Aug13 Quasar data brought up to publications as at 10 August 2013, including SDSS-DR10. Note that the DR10 is an automated catalog, so its object classifications are not as trustworthy as manual classifications. Thus, earlier manual classifications are retained over DR10 classifications. XMM-Newton X-ray data updated to 3XMM-DR4 version (24-July-2013). FIRST radio data updated to 13Jun05 version (05-June-2013). 3.6 23Oct13 Quasar data brought up to publications as at 22 October 2013. Two additional columns of radio/X-ray detections were added. This is so that any radio lobes will always be fully displayed, and extra detections from other source catalogs give a sense of fuller coverage. 158 additional quasars were added from SDSS-DR10. These were flagged as bad astrometry, but they are confirmed by the author's optical background database. Photometric quasar candidates from surveys other than NBCKDE and XDQSO, e.g., SWIRE, have been dropped because much of their yield are type 2. This includes Palanque-Delabrouille et al. (2011,A&A,530,122), which has been well investigated spectroscopically and its residue thus less likely to be QSOs. X-ray detections from the Champ2 catalog, Kim M. et al, 2007,ApJS,169,401 have been removed. It's a small catalog which, unlike others, does not present its raw astrometry needed for calculating optical solutions. The Veron quasar catalog v13 (2010 A&A,518A,10) included some objects denoted as non-quasars by their discovery papers, and the following have been removed as a result: (a) 484 emission-line galaxies (ELGs) of z<0.46 from Schneider/Schmidt/Gunn 1994,AJ,107,1245, incorporated as QSOs by VCV13; (b) 55 ELGs of Schneider/Schmidt/Gunn 1999,AJ,117,40; (c) 58 galaxies from 2dF-GRS (Colless M. et al., astro-ph/0306581); and (d) 41 galaxies from La Franca F. et al., 1999,A&AS,140,351. A few positional fixes, de-duplications, and removals of type-2s. 3.7 26Nov13 Quasar data brought up to publications as at 26 November 2013, including the SDSS DR10Q release by Isabelle Paris et al, 2013 arXiv:1311.4870. 318 SDSS "quasars" of auto-redshift>4 which were not subsequently confirmed by visual inspection are removed as bogus (communication Adam Myers). The Veron quasar catalog v13 (2010 A&A,518A,10) flagged some objects as questionable in their "spec" field. These have unclear spectra or are described as "possible" by their discovery papers. 178 of these are removed, and 52 such BL Lacs with redshift>0.5 are re-classed to AGNs. Some positional fixes and de-duplications of individual objects. 3.8 16Feb14 Quasar data brought up to publications as at 15 February 2014. NBCKDE and BOSS quasar likelihoods have been calibrated against the DR10Q (Paris I. et al, 2013 arXiv:1311.4870) classifications. The Swift X-ray Point Source catalog (Evans P.A. et al, 2014,ApJS,210,8) is added to the background data, resulting in 12604 associations. 110 SDSS-DR10 automated survey objects are removed as artefacts. De-duplication of radio/X-ray detections improved. 3.9 30Jun14 Quasar data brought up to publications as at 30 June 2014. The XMM-Newton Slew Survey source catalog release 1.6 was added to X-ray data. The 1SXPS X-ray detections were being dropped; this was fixed and 21268 were included as a result. The Veron-Cetty & Veron Quasar Catalog (VCV) 13th edition (2010,A&A,518,10) was fully mapped into optical; corrections from this were incorporated. 4.0 05Aug14 Quasar data brought up to publications as at 5 August 2014. The threshold for inclusion of QSO candidates was raised to 80% confidence. This resulted in the loss of ~240,000 objects from v3.9, but it improved the confidence of use. XAssist v4 XMM-Newton and Chandra X-ray data was updated to 21-July-2014. 98 entries were found to be type II or not quasars, and so removed. The catalog layout was changed to conform better to the NED guide "Best Practices for Data Publication" by Marion Schmitz et al (v1.2, 2013) in these ways: (a) all citations were changed to original discovery papers and no longer to VCV 13th edition or to NED and discovery citations are now indexed in a separate file; (b) quasar and radio/X-ray names which used to run together have been corrected to adhere to naming standards. 4.1 20Oct14 Quasar data brought up to publications as at 5 October 2014. The input values of RA and DEC used for this table were given in degrees rather than sexagesimal.Type 2 objects were included for the convenience of the users, but completeness of these is only about 95%. The type I objects are believed to be 100% complete from the literature. About 3000 SDSS "quasars" were removed as not quasars. These were auto-objects which were not taken up by the manual Paris files, and which were not given a subclass by the SDSS pipeline -- thus, the lowest quality objects. Another 2000 were reclassified as AGN or type 2 in this catalog. VCV mis-copied the redshifts from 2008 A&A,488,417 -- now fixed. QSOs & AGN re-partitioned by psf class and modified luminosity equation. Miscellaneous tweaks and fixes done when revealed by publication-related analysis. 4.2 06Dec14 Quasar data brought up to publications as at 6 December 2014. SDSS DR10/DR10Q and DR7/DR7Q data were reprocessed, yielding a few more quasars and using the DR10Q redshifts more as the current standard. Further adjustments were made to the luminosity equation separating QSOs from AGN, resulting in about 2000 AGN reclassified as QSOs. 18 new quasars from Dan Weedman, based on his re-analysis of the Weedman 1985 spectra in combination with NBCKDE photometric redshifts for those objects. 4.3 11Jan15 Quasar data brought up to publications as at 10 January 2015, including the newly-released SDSS-DR12 and SDSS-DR12Q (www.sdss.org). Approximately, 800 quasars sourced from the AGES catalog, Kochanek et al. (2012, ApJS, 200, 8). Approximately, 200 extra quasars added in a full round-up from NED and SIMBAD. 4.4 06Feb15 See list of changes above.
Flesch, E. The Million Quasars (MILLIQUAS) Catalog, Version 4.4 (6 February 2015) http://quasars.org/milliquas.htmSee also:
APM Catalog http://www.ast.cam.ac.uk/~mike/apmcat USNO-A/B Catalogs http://www.nofs.navy.mil NVSS Catalog http://www.cv.nrao.edu/nvss FIRST Catalog http://sundog.stsci.edu SUMSS Catalog http://www.physics.usyd.edu.au/sifa/Main/SUMSS MGPS Catalog http://www.physics.usyd.edu.au/sifa/Main/MGPS2 ROSAT Catalogs http://www.mpe.mpg.de/xray/wave/rosat/catalogue http://www.mpe.mpg.de/xray/wave/rosat/rra/ 1WGA Catalog http://wgacat.gsfc.nasa.gov/wgacat/wgacat.html Chandra Source Catalog http://cxc.cfa.harvard.edu/csc/ XAssist Home Page http://xassist.pha.jhu.edu/zope/xassist XMM-Newton Catalog http://xmmssc-www.star.le.ac.uk XMM-Newton Slew Survey http://www.star.le.ac.uk/~amr30/Slew
(1) pQSO, the probability that the candidate is a true QSO.
NBCKDE compares QSO & star density profiles per object to obtain a nominal pQSO. XDQSO is annotated with a nominal pQSO which their paper cautions is just a comparative figure and not a genuine QSO likelihood (see esp. their figure 14). In this "Million Quasars" catalog, the requirement is to display genuine odds for each candidate that it is indeed a quasar. The recent manual DR10Q catalog (Paris I. et al, 2014, A&A, 563, 54) provides ~100K spectral classifications for these candidates by which the XDQSO/NBCKDE pQSO-pcts can be calibrated into accurate DR10-based QSO-pcts via a simple mapping. Individual notes per catalog:
BOSS candidates: These are XDQSO flagged with good=0 (which means good). The author finds that that BOSS pQSO-pcts map to true QSO-pcts by (1) subtract 14, and (2) for pQSO>90, also add (pQSO-90), and (3) for pQSO>94, also add 0.5*(pQSO-94). This mapping yields the following alignment to DR10Q findings:
XDQSO QSO-pct DR10Q DR10Q DR10Q pQSO bin bin of 5 #objs QSOs QSOpct ------ -------- ----- ----- ----- 64 50 679 349 51.4 69 55 1088 622 57.2 74 60 1708 1002 58.7 79 65 2850 1844 64.7 84 70 5176 3611 69.8 89 75 7033 5265 74.9 92 80 5832 4662 79.9 94.5 85 7208 6163 85.5 96.5 90 10392 9383 90.3 98.5 95 20646 19837 96.1 99.8 98-99(max) 16830 16552 98.3
NBCKDE candidates: These are a lower-yield subset of NBCKDE, as outlined above. This truncated data is not as well-behaved as the BOSS data, but a simple map of NBCKDE pQSO-pcts to true QSO-pcts to (1) subtract 25, and (2) for pQSO>92, also add 1.5*(pQSO-92), and (3) for pQSO>98, also add 2.5*(pQSO-98). This yields:
NBCKDE QSO-pct DR10Q DR10Q DR10Q pQSO bin bin of 5 #objs QSOs QSOpct ------ -------- ----- ----- ----- 75 50 140 84 60.0 80 55 357 204 57.1 85 60 803 497 61.9 90 65 5884 3739 63.5 93 70 5415 3723 68.8 95 75 4195 3123 74.4 97 80 2003 1588 79.3 98.5 83-84(max) 878 750 85.4
XDQ candidates: These are XDQSO flagged with good>0 (which means not good). SDSS-3 deemed these objects too faint (etc) to use as BOSS targets. However, high-pQSO objects still have good yields although DR10Q has only ~150 of these. The author finds an adequate mapping is QSOpct = 15 + 0.75*pQSO, but the data lose their coherence below QSOpct=80 so objects are excluded below there. This yields:
XD-faint QSO-pct DR10Q DR10Q DR10Q pQSO bin bin of 5 #objs QSOs QSOpct ------ -------- ----- ----- ----- 88 80-82 8 5 62.5 93.5 85 25 23 92.0 99 88-90(max) 87 75 86.2
(2) photometric redshifts.
NBCKDE provides photometric "most likely" redshifts as the weighted average of a bounded range for each candidate. XDQSO has not published redshifts, so these have been calculated using a training set of 199751 quasars from SDSS-DR9, binning the 4 colors by 0.1z, then using rainflow analysis to cluster the redshift bins for each XDQSO candidate. The outcome is similar to NBCKDE redshifts, as seen in a test using SDSS-DR10 quasars which were not in the training set. This comparison of 22919 NBCKDE & rainflow & SDSS-DR10 QSO redshifts is listed at http://quasars.org/docs/NBCKDE-MQ-redshifts.txt, which treats each photometric redshift as a "hit" if within 0.5z of the true spectral redshift.
There it is seen that the NBCKDE hit rate is 16658/22919 = 72.7%, and the rainflow hit rate is 16986/22919 = 74.1%. No doubt the NBCKDE method is better than this simple algorithm, but the author had the advantage of the very large SDSS-DR9 training set. This good performance validates the inclusion of these redshifts.
The designation of the source as taken from the literature. A "BOSS" prefix indicates an XDQSO BOSS target (XDQSO good=0). An "XDQ" prefix is an XDQSO non-BOSS object (XDQSO good=1,2). Nameless radio/X-ray associated objects here display the J2000 position in "HHMMSS.S+DDMMSS" for the convenience of the user. If needing a name for it, just prefix this value with "MQ", e.g., MQ J000001.5-251706. Use the ref_name parameter and the J2000.0 equatorial coordinates to make an IAU-style name: catalog QO=QORG, AX=ARXA, MQ=MQ. For example: a source at 00 00 01.6 -25 17 07 with ref_name of 'AX' would be 'ARXA J000001.6-251707'.
The Right Ascension of the quasar candidate in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-7 degrees in the original table.
The Declination of the quasar candidate in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-7 degrees in the original table.
The Galactic Longitude of the quasar candidate.
The Galactic Latitude of the quasar candidate.
The classification of the object, where the following abbreviations are used:
Q = QSO from the literature, broad-line unresolved. 424748 of these. A = AGN, extended/Seyferts/low-luminosity. 26623 of these. B = BL Lac object, 1595 of these. q = photometric quasar candidates, SDSS-based, 612203 of these. K = type II objects, 32783 of these included for user reference. R = Radio association displayed. X = X-ray association displayed. 2 = Double radio lobe declaration (declared by data-driven algorithm).
The red optical magnitude of the object. The type and source of this magnitude is specified in the optical_flag parameter value. Optical data are from the APM (http://www.ast.cam.ac.uk/~mike/apmcat/), USNO-A & USNO-B (http://www.nofs.navy.mil/), and the SDSS (http://sdss3.org/). Magnitudes have been recalibrated from the original APM/USNO-A values (which are POSS-I or UKST identified in the description for the optical_flag parameter) as documented in QORG (2004, A&A, 427, 387). Calibrated USNO-A magnitudes are often retained in preference to USNO-B. APM galaxies brighter than 17th magnitude are usually represented as far too bright due to PSF modeling. If the optical_flag parameter value contains r/b/g/i/v/u/z, then the magnitudes are from the object's source catalog, e.g., SDSS, 2QZ, etc. Note that many SDSS magnitudes are extinction-corrected ~0.3 mag brighter than photometry.
The blue optical magnitude of the object. The type and source of this magnitude is specified in the optical_flag parameter value. Optical data are from the APM (http://www.ast.cam.ac.uk/~apmcat/), USNO-A & USNO-B (http://www.nofs.navy.mil/), and the SDSS (http://sdss3.org/). Magnitudes have been recalibrated from the original APM/USNO-A values (which are POSS-I or UKST identified in the description for the optical_flag parameter) as documented in QORG (2004, A&A, 427, 387). Calibrated USNO-A magnitudes are often retained in preference to USNO-B. APM galaxies brighter than 17th magnitude are usually represented as far too bright due to PSF modeling. If the optical_flag parameter value contains r/b/g/i/v/u/z, then the magnitudes are from the object's source catalog, e.g., SDSS, 2QZ, etc. Note that many SDSS magnitudes are extinction-corrected ~0.3 mag brighter than photometry.
This field contains coded information on the optical source properties, as follows:
p = optical magnitudes are POSS-I O (violet 4100A) and E (red 6500A). These are preferred because O is well-offset from E, and these plates were always taken on the same night, thus the red-blue color is correct even for variable objects. j = blue magnitude is SERC J (Bj 4800A blue-green) from the POSS-II or UKST surveys. Red-blue color is less reliable because the plates were taken in different epochs, i.e. years apart. g = blue magnitude is SDSS green 4900A. u = blue magnitude is SDSS ultraviolet 3850A. b = blue magnitude is Vega 4400A. v = red magnitude is visual, ie, white, 5500A midpoint. i = red magnitude is infrared 7500A. z = red magnitude is infrared z 8500A. k = red magnitude is infrared k 22000A. (not v/i/z/k) = standard red color 6500A. + = variability nominally* detected for both red & blue. m = proper motion nominally* detected. a = object is an SDSS galaxy with AGN subclass. If also BROADLINE then Milliquas class is 'A', otherwise 'K' (see broad_type). ? = identification uncertain (quasar may be located elsewhere). (*) from USNO-B or Flesch & Hardcastle (2004, A&A, 427, 387), section A.1 end
A coded representation for the point spread function (PSF) of the optical source in the red. The APM, USNO-B, and SDSS provide PSF class, albeit using different criteria. The codes are as follows:
- = point source / stellar PSF (APM notation: -1, here truncated) 1 = fuzzy / galaxy shape (APM notation: 1 and some 2) n = no PSF available, whether borderline or too faint to tell, etc. x = not seen in this color (fainter than plate depth, or confused, etc.)
A coded representation for the point spread function (PSF) of the optical source in the blue. The APM, USNO-B, and SDSS provide PSF class, albeit using different criteria. The codes are as follows:
- = point source / stellar PSF (APM notation: -1, here truncated) 1 = fuzzy / galaxy shape (APM notation: 1 and some 2) n = no PSF available, whether borderline or too faint to tell, etc. x = not seen in this color (fainter than plate depth, or confused, etc.)
The redshift of the object, taken from the literature as specified in the ref_redshift parameter. Photometric most-likely redshifts are rounded here to 0.1 z. The photometric redshifts provided by this catalog are discussed in the Section "Inclusion of SDSS Photometric QSO Candidates into MILLIQUAS" above.
A numerical code for the literature reference from which the name was taken. Refer to the accompanying file which lists all citations in sequence. Each row has 4 columns; these are:
(a) the citation number as it appears in the data; (b) the count of times used as a citation for the name (excluding type 2); (c) the count of times used as a citation for the redshift (excl. type 2); (d) the citation, i.e., standard authors list, year, journal volume & page, and sometimes a brief description or website.
A numerical code for the literature reference from which the redshift was taken, using the same rubric as used for the ref_name parameter (q.v.).
For a QSO candidate (type starting with q/R/X/2), this field contains the nominal probability that this object is a QSO, in percent, based on photometric and/or radio/X-ray association analysis. For a known QSO (type starting with Q/A/B/K), this field contains the percent chance that the shown radio/X-ray detection(s) is truly associated to it.
Candidates (objects without spectroscopic confirmation) are included where calculated at 80%+ probability of being true quasars. Two families of calculated objects are included:
(1) Photometric quasars, mostly from the SDSS-based NBCKDE/XDQSO catalogs, totaling 612,203 of which 39,721 also show radio/X-ray association. The displayed probability of NBCKDE/XDQSO objects is not from their catalogs which provide data ratios only; instead, the displayed absolute probability is calculated as described in the Section "Inclusion of SDSS Photometric QSO Candidates into MILLIQUAS" above.
(2) Radio/X-ray associated objects, totaling 53,059 without any other attribution. The displayed probability is calculated as described in the ARXA/QORG papers.
39,721 photometric quasars are also radio/X-ray associated, and the displayed probability figure combines the photometric QSO probability P1 and the radio/X-ray derived QSO probability P2 as
P = 1/(1+((1-P1)*(1-P2))/(P1*P2)).Using the probability, as expected, these 1,116,633 type-I objects will yield 1,066,833 actual quasars, making this a true million quasars catalog.
The identification of the radio source associated with the quasar candidate, if any.
This is usually the identification of the X-ray source associated with the quasar candidate, if any, but it can also be the identification of a radio lobe, if the radio_name parameter for the object itself contains the name of a radio lobe.
Radio/X-ray detections come from the following catalogs (and their respective home pages):
FIRST: VLA FIRST survey, 13Jun05 version, http://sundog.stsci.edu NVSS: NRAO VLA sky survey, http://www.cv.nrao.edu/nvss SUMSS: Sydney U. Molonglo, http://www.physics.usyd.edu.au/sifa/Main/SUMSS MGPS: Molonglo galactic plane survey, same attribution as SUMSS ROSAT catalogs home page: http://www.mpe.mpg.de/xray/wave/rosat/catalogue -- 1RXH: ROSAT HRI (high resolution imager) -- 1RXS: ROSAT RASS (all-sky survey, both bright & faint) -- 2RXP/2RXF: ROSAT PSPC (position sensitive proportional counter) 1WGA: White, Giommi & Angelini, http://wgacat.gsfc.nasa.gov/wgacat/wgacat.html CXO: Chandra Source Catalog, http://cxc.cfa.harvard.edu/csc CXOX: XAssist Chandra source list, http://xassist.pha.jhu.edu/zope/xassist 3XMM: XMM-Newton, http://xmm.esac.esa.int/xsa XMMSL: XMM-Newton Slew survey, http://xmm.esac.esa.int/xsa XMMX: XAssist XMM-Newton source list, http://xassist.pha.jhu.edu/zope/xassist 1SXPS: Swift X-ray Point Source catalog, http://www.swift.ac.uk/1SXPS Optical field solutions are calculated from the raw source positions of all these catalogs as described in the author's ARXA paper (2010,PASA,27,283).
The identification of the radio lobe or an additional radio or X-ray identification associated with the quasar candidate, if any.
An additional identification of the radio lobe or an extra X-ray identification associated with the quasar candidate, if any.
The HEASARC Browse object classification, based on the information given in the broad_type parameter.