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MILLIQUAS - Million Quasars Catalog, Version 4.5 (10 May 2015)

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Overview

This table contains the Million Quasars (MILLIQUAS) Catalog, Version 4.5 (10 May 2015). It is a compendium of all type-I QSOs and AGN, and BL Lac objects, complete from the literature through January 2015 and from NED and SIMBAD up to 9 May 2015. High-confidence (80%+) photometric SDSS and radio/X-ray associated candidates are included, plus type-II objects, which brings the total number of objects to 1,153,110. Objects have been de-duplicated across multiple source catalogs. Each object is presented with the original name, best redshift, and astrometry (accurate to 1-2 arcsec, fixed onto optical APM/USNO-B/SDSS combined data).

This version has the following changes from the previous edition:

(1) 780 new quasars from LAMOST-DR1 (Luo et al. 2015, arXiv:1505.01570) have
    been added. LAMOST-DR1 is a pipeline catalog with much provisional data,
    so the author has selected the best-eligible objects only. LAMOST plans a
    manual (reliable) QSO catalog later this year. Also, NED/SIMBAD quasar
    data is included up to 9 May 2015.
(2) Citations have been greatly simplified, referencing the recently
    published Half Million Quasars catalog (HMQ: Flesch E., 2015 PASA,32,10,
    arXiv:1502.06303) for smaller legacy citations while still citing large
    surveys like SDSS and 2QZ. The legend for the citations is given below,
    and the separate citations file is no longer needed.
(3) 3XMM-DR5 (Rosen et al., 2015, arXiv:1504.07051) included in X-ray data.
    Also, high-confidence data from 2XMMi-DR3 is included, as acknowledged in
    section 8.2 of the Rosen paper (dropped 2XMMi-DR3 data recognized as
    valid).
(4) Minor fixes to optical data have resulted in a few more radio/X-ray
    associations.
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.

Questions/comments/praise/complaints may be directed to Eric Flesch at eric@flesch.org. 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/.

Version Log:

     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  Quasar data brought up to publications as at 25 January
                   2015. Some reprocessing of the SDSS-DR12 and SDSS-DR12Q
                   data. About 1000 type-1 objects reclassified to type-2.
                   Photometric candidate likelihoods and redshifts were
                   recalibrated using the SDSS-DR12Q quasars as the benchmark.
     4.5  10May15  See list of changes above.

References

Flesch, E.
    The Million Quasars (MILLIQUAS) Catalog, Version 4.5 (10 May 2015)
    http://quasars.org/milliquas.htm
See 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

Provenance

This table was updated by the HEASARC in May 2015 based on a machine-readable catalog obtained from the author's MILLIQUAS website at http://quasars.org/milliquas.htm after he notified the HEASARC that a new version was available.

Inclusion of SDSS Photometric QSO Candidates into MILLIQUAS

The two major releases of SDSS photometric QSO candidates are the NBCKDE catalog (Richards G.T. et al., 2009, ApJS, 180, 67) taken over the DR6 footprint, and the XDQSO catalog (Bovy J. et al., 2011, ApJ, 729, 141) over the DR8 footprint, which provides targets for the SDSS BOSS survey plus a set of fainter objects. Shared objects are here reported as XDQSO because of its larger footprint, else XDQSO would have a different data profile in the DR6 footprint compared with the DR8 extension. Thus the NBCKDE data reported here is minus those shared objects -- a subset with a lower yield ratio than that of the full NBCKDE data. This MILLIQUAS catalog adds pQSO and redshift calculations to these:

(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.


Parameters

Name
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'.

RA
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.

Dec
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.

LII
The Galactic Longitude of the quasar candidate.

BII
The Galactic Latitude of the quasar candidate.

Broad_Type
The classification of the object, where the following abbreviations are used:

       Q = QSO from the literature, broad-line unresolved. 425527 of these.
       A = AGN, extended/Seyferts/low-luminosity. 26626 of these.
       B = BL Lac object, 1595 of these.
       q = photometric quasar candidates, SDSS-based, 611772 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).
  

Rmag
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.

Bmag
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.

Optical_Flag
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
  

Red_PSF_Flag
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.)
  

Blue_PSF_Flag
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.)
  

Redshift
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.

Ref_Name
A character code for the literature reference from which the name was taken.

       2QZ (23008,19654): Croom S.M. et al., 2004,MNRAS,349,1397
       2SLAQ (7747,6550): Croom S.M. et al., 2009,MNRAS,392,19
       ARXA (9352,0): Atlas of Radio/X-ray Associations, Flesch E., 2010,PASA,27,283
       DR12 (20942,30824): Alam S. et al., 2015, arXiv:1501.00963, http://sdss.org/dr12
       DR12Q (278151,301872): SDSS-DR12Q, Paris I. et al., 2015, paper in preparation,
              files at http://data.sdss3.org/sas/dr12/boss/qso/DR12Q
       DR7 (17520,16817): SDSS DR7, Abazajian K.N. et al., 2009,ApJS 182,543,
              files at http://classic.sdss.org/dr7/products/spectra/getspectra.html
       DR7Q (93818,80339): SDSS Quasar DR7, Schneider D. et al., 2010,AJ,139,2360
       HMQ (31258,29485): Half Million Quasars catalog, Flesch E., 2015,PASA,32,10,
                          also  arXiv:1502.06303
       LAMOST (780,780): LAMOST-DR1, Luo A.-L. et al., 2015, arXiv:1505.01570
       MQ (32979,254433): MILLIQUAS, original data in this catalog, Flesch E.,2015
       NBCKDE (57191,344229): Richards G.T. et al., 2009,ApJS,180,67
       NED (2,2): NASA/IPAC Extragalactic DB, http://ned.ipac.caltech.edu
       PGC (13306,8): Principal Galaxy Catalogue, Paturel G. et al., 2003,A&A,412,45
       QORG (12476,0): QORG, Flesch E. and Hardcastle M., 2004,A&A,427,387
       SIMBAD (0,0): SIMBAD Astronomical DB, http://simbad.u-strasbg.fr/simbad
       XDQSO (554574,0): SDSS-XDQSO, Bovy J. et al., 2011,ApJ,729,141
  

Ref_Redshift
A character code for the literature reference from which the redshift was taken, using the same rubric as used for the ref_name parameter (q.v.).

QSO_Prob
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 611,772 of which 40,297 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 54,807 without any other attribution. The displayed probability is calculated as described in the ARXA/QORG papers.

40,297 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 1,118,732 type-I objects will yield 1,068,841 actual quasars, making this a true million quasars catalog.

Radio_Name
The identification of the radio source associated with the quasar candidate, if any.

Xray_Name
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
       2XMM/2XMMi: XMM-Newton DR3, http://xmm.esac.esa.int/xsa/versions.shtml
       3XMM: XMM-Newton DR5, http://xmm.esac.esa.int/xsa
       XMMSL: XMM-Newton Slew Survey v1.6, 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).
  

Alt_Name_1
The identification of the radio lobe or an additional radio or X-ray identification associated with the quasar candidate, if any.

Alt_Name_2
An additional identification of the radio lobe or an extra X-ray identification associated with the quasar candidate, if any.

Class
The HEASARC Browse object classification, based on the information given in the broad_type parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 18-May-2015