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MILLIQUAS - Million Quasars Catalog, Version 5.4 (17 October 2018)



This table contains the Million Quasars (MILLIQUAS) Catalog, Version 5.4 (17 October 2018). It is a compendium of 618,837 type-I QSOs and AGN, largely complete from the literature through 15 October 2018, including the release of SDSS-DR14Q and LAMOST DR4. Also included are ~1,320,000 high-confidence (80%+ likelihood) quasar candidates from the NBCKDE, NBCKDE-v3, XDQSO, AllWISE and Peters photometric quasar catalogs and from all-sky radio/X-ray associated objects which are calculated by the author. Type-II and BL Lac objects are also included, bringing the total count to 1,982,686. Objects have been de-duplicated across multiple source catalogs. Each object is presented with its original name, best redshift, and 0.1-arcsecond-accurate astrometry (sourced from optical APM/USNO-B/SDSS data).

Low-confidence or questionable objects (so deemed by their researchers) are not included in Milliquas. Additional quality cuts are applied as detailed in Flesch 2015, PASA, 32, 10. Some multiple lensed images (very incomplete) are included as type='L' with only the brightest one recorded as type='Q'. The aim here is to present one unique reliable object per each data row.

This version has the following changes from the previous edition:

(1) Quasars from individual papers from August 2017 forward to 15 October 2018
    have been added, plus some from a couple older papers.
(2) Quasar doublets are more carefully processed to show 2 quasars instead of 1.
    Discoverers don't always publish the positions of both.
(3) A few gravitiationally lensed images are added as type='L', additional to
    the already-catalogued brightest one.  These are added only where my optical
    data shows them, to account for any radio/X-ray associations to them.
(4) The 3XMM-DR8 X-ray source catalog (
    has been added and new X-ray associations calculated.
(5) A bug in v5.3 dropped radio/X-ray associations to some high-z quasars; now
The contents are relatively simple; each object is shown as one entry with the sky coordinates, its original name, object class, red and blue optical magnitudes, PSF class, redshift, the citations for the name and redshift, and up to four radio/X-ray identifiers where applicable.

Questions/comments/praise/complaints may be directed to Eric Flesch at If you use this catalog in published research, the author requests that you please cite it. The citation for the Milliquas catalog is Flesch E., 2015, PASA, 32, 10, which was the published version of this catalog after the release of SDSS-DR12.

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 made use of the SIMBAD database, operated at CDS, Strasbourg, France.

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   3Aug09  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,
     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.,
                   A few positional fixes, de-duplications, and removals of
     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
                   artifacts. De-duplication of radio/X-ray detections
     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
     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 ( 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  780 new quasars from LAMOST-DR1 (Luo et al. 2015,
                   arXiv:1505.01570) were added. LAMOST-DR1 is a pipeline
                   catalog with much provisional data, so the author 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. Citations were
                   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. A
                   legend for the citations is given below, and the separate
                   citations file is no longer needed as a result of this.
                   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). Minor
                   fixes to optical data resulted in a few more radio/X-ray
     4.6  30Nov15  Additional QSO candidates were sourced from the new
                   NBCKDE v3 catalog (Richards G.T. et al., 2015-ApJS-219-39)
                   and a variability and refraction sourced catalog (Peters
                   C.M. et al., 2015-ApJ-811-95). These added about 300,000
                   new candidates to Milliquas. Note that the NBCKDE v3
                   catalog uses different selection criteria from its
                   predecessor, and so augments it rather than superseding
                   it. The threshold for inclusion of QSO candidates was
                   raised from 80% QSO-likelihood to 90%, so the catalog
                   should be reliable even for spot checks. NED and SIMBAD
                   listed quasars were included through 30-Nov-2015.
     4.7  02Mar16  527 new QSOs were added from recent publications, including
                   33 new QSOs with z>5 of which 4 have z>6. The UV-Bright
                   Quasar Survey (UVQS, T.R. Monroe et al, arXiv:1602.06255)
                   was included with two mag-14 and 43 mag-15 QSOs plus many
                   brighter AGN.
     4.8  22Jun16  The Chandra ACIS source catalog (Wang S. et al.,2016,ApJS,
                   224,40) was added and new X-ray associations calculated.
                   The 2nd RASS source catalog 2RXS (Boller Th. et al., 2016,
                   A&A,588,103) replaced 1RXS for the most part, with
                   significant differences in places. Radio/X-ray processing
                   was tightened and data recalibrated to improve likelihood
                   reliability, as part of a new radio/X-ray catalog in
                   preparation. 23,727 radio/X-ray associated objects, recently
                   dropped, were restored on the criterion that they are each
                   80%+ likely to be true quasars. This was done because this
                   information is not found elsewhere.
     4.8b 30Jul16  The 3XMM-DR6 X-ray source catalog was added and new X-ray
                   associations calculated. The radio/X-ray data have been
                   reprocessed in line with that of the Million Optical
                   Radio/X-ray (MORX) Associations Catalog (Flesch 2016,
                   PASA, 33, 52).
     5.0  19Jun17  The J2000 coordinates now have 1/10th arcsecond precision,
                   and the magnitudes have 1/100th mag precision, either from
                   the original surveys or from the All-Sky Portable (ASP)
                   optical catalog (arXiv:1705.05434). 5414 net QSOs/AGNs were
                   added from recent surveys (listed below), notably AAOz,
                   OzDES, LAMOST DR2, and a reload of AGES. The 3XMM-DR7 and
                   XMMSL2-2.0 Slew X-ray source catalogues were added and new
                   X-ray associations calculated. A few duplicates were
                   removed. Notably, SDSS J131715.46+601533.1 was found to be
                   a duplicate of SBS 1315+605.
     5.1  30Jun17  Included full coverage of the Subaru-XMM Deep Field from
                   multiple authors, LAMOST DR3, and other miscellaneous
     5.2  05Aug17  SDSS-DR14 and SDSS-DR14Q were added, using the processing
                   rules from the Half Million Quasars catalog (HMQ: Flesch
                   2015, PASA, 32, 10). WISE quasar candidates were added
                   from Secrest et al. 2015, ApJS, 221, 12. These are
                   ~430,000 candidates over the whole sky for which 2-color
                   optical objects were found within a 2-arcsec radius. They
                   were processed into pQSOs from calibration against the
                   SDSS-DR12Q multi-class superset, and photometric redshifts
                   obtained using the four-color based method from the HMQ
                   Appendix 2. The four colors used were B-R, R-W1, W1-W2,
                   and W2-W3. Type-II narrow emission-line galaxies (NELGs,
                   class='N') were added as the luminosity class
                   corresponding to the type-I AGN galaxies. High-luminosity
                   type-II NLAGN (class='K') correspond to the type-I
                   quasars. The NLAGN/NELG divider is the same luminosity/psf
                   function which separates QSOs from AGNs. Type-II NELGs
                   include unquantified contamination by LINERs and probably
                   a few starbursts which eluded removal, so it serves as a
                   catch-all category presented for completeness, rather than
                   as a strict type-II class. Small publications through 5
                   August 2017 were added. Positional fixes (of about 2
                   arcsec) were applied to ~150 objects.
     5.3  12Sep18  Radio/X-ray association likelihoods calculated to a
                   granularity of 1/10th of an arcecond for Chandra,
                   XMM-Newton, and Swift X-ray source catalogs and the FIRST
                   radio source catalog. All associations have been
                   recalculated onto the APM/USNO-B optical background of
                   Flesch 2017,PASA,34,25 (Figure 3). Radio/X-ray association
                   likelihoods to faint SDSS sources not in the optical
                   background were previously halved, based on the
                   approximately doubled sky density of SDSS. This deduction
                   was changed to be classed by PSF and red-blue color,
                   consequentially most SDSS likelihoods were reduced more,
                   often by 60%-90%. Associations to other faint objects were
                   also reduced. The overall effect was that ~20,000
                   candidates fell below the 80% likelihood threshold for
                   inclusion in Milliquas, and so were removed. Visually
                   inspected quasars from the LAMOST DR3Q (Dong et al.,
                   2018,AJ,155,189) and auto-quasars from the LAMOST DR4
                   ( were quality checked and a total
                   of 10,624 quasars/AGN added to Milliquas.
     5.4  17Oct18  See list of changes above.


Flesch, E.
    The Million Quasars (MILLIQUAS) Catalog, Version 5.4 (17 October 2018)
See also:
   APM Catalog    
   USNO-A/B Catalogs
   NVSS Catalog   
   FIRST Catalog  
   SUMSS Catalog  
   MGPS Catalog   
   ROSAT Catalogs 
   1WGA Catalog   
   Chandra Source Catalog
   XAssist Home Page
   XMM-Newton Catalog
   XMM-Newton Slew Survey


This table was updated by the HEASARC in October 2018 based on a machine-readable catalog obtained from the author's MILLIQUAS website at


The designation of the source as taken from the literature. Nameless radio/X-ray associated objects here display the J2000 position in "HHMMSS.SS+DDMMSS.S" for the convenience of the user. If needing a name for it, just prefix this value with "MQ ", e.g., MQ J000001.64-251706.3.

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, type I broad-line unresolved, 592328 of these.
       A = AGN, type I Seyferts/host-dominated, 26509 of these.
       B = BL Lac object, 1615 of these.
       q = photometric quasar candidate from SDSS or WISE, 1266905 of these.
       L = lensed quasar extra image, very incomplete, only 9 so far.
       N = type-II narrow-line Seyfert/NELG galaxy, 37425 of these.  This class
                includes an unknown number of LINERs, presented for completeness.
       K = type-II narrow-line NLAGN, quasar-like high luminosity, 2079 of these.
       R = Radio association displayed.
       X = X-ray association displayed.
       2 = Double radio lobes displayed (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 (, USNO-A & USNO-B (, and the SDSS ( 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. Integer magnitudes (e.g., 22.00) can be estimates if both bands are integer or one band empty. 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 observed.

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 (, USNO-A & USNO-B (, and the SDSS ( 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. Integer magnitudes (e.g., 22.00) can be estimates if both bands are integer or one band empty. 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 4050A) and E (red 6400A).
           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 4850A 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, red is SDSS r 6200A.
       u = blue magnitude is SDSS ultraviolet 3850A.
       b = blue magnitude is Vega 4400A (Johnson).
       v = red magnitude is visual, i.e., white, 5500A midpoint.
       i = red magnitude is infrared 7500A.
       z = red magnitude is infrared z 8500A.
       (not v/i/z) = standard red 6400A (Cousins).
       + = variability nominally detected in both red/blue over multi-epoch data.
       m = proper motion nominally detected, from USNO-B.
       a = object is an SDSS galaxy with AGN subclass.  If also BROADLINE then
           Milliquas class is 'A', otherwise 'N' (see broad_type).
       ? = identification uncertain (quasar may be located elsewhere, 4 of these).

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 redshifts (for objects classified as 'q') are rounded to 0.1 z. The XDQSO catalog does not provide photometric redshifts, so those are provided either by NBCKDE or by this catalog using the method detailed in Appendix 2 of the author's HMQ paper (2015, PASA, 32, 10). AllWISE photometric redshifts are similarly calculated using the four colors B-R, R-W1, W1-W2, and W2-W3, and are displayed where calculated as 50%+ (usually 80%+) likely to be true within 0.5z of the displayed redshift value.

A character code for the literature reference from which the name was taken, as indicated below. There are also a few numerical codes, the meanings of which can be found in the online version of the author's Half Million Quasars Catalog (HMQ: Flesch 2015, PASA, 32, 10) at

       Code (No. of names, No. of redshifts)   Reference

       2dF (366,232): 2dF galaxy survey, Colless M. et al., 2001,MNRAS,328,1039
       2QZ (27515,24161): Croom S.M. et al., 2004,MNRAS,349,1397
       2SLAQ (10387,8716): Croom S.M. et al., 2009,MNRAS,392,19
       3LAC (30,28): Fermi AGN v3, Ackermann M. et al., 2015,ApJ,810,14
       3XLSS (25,25): The XXL Survey, Pierre M. et al., 2016,A&A,592A,1P
       6dF (287,227): 6dF galaxy survey, Jones D.H. et al., 2009,MNRAS 399,683
       AAOz (1491,1498): AAOmega XXL-South: Lidman C. et al., 2016,PASA,33,1
       AGES (2047,2047): AGES survey, Kochanek C.S. et al., 2012,ApJS,200,8
       AGNELA (1,1): SDSS J1433+6007 4-lens, Agnello A. et al., 2018,MNRAS,474,3391
       AGNEL2 (13,13): VST-Gaia QSO pairs, Agnello A. et al., 2018,MNRAS,475,2086
       AGNELL (1,1): quad lens in v, Adriano Agnello, 2018,arXiv:1805.10296
       ALMA (4,4): ALMA hi-z, Roberto Decarli R. et al., 2018,ApJ,854,97
       ATel (4,4): Astronomers Telegraph posts held on
       ATLAS (229,269): Mao M.Y. et al., 2012,MNRAS,426,3334
       BAHM (24,24): dust-reddened qSOs, Banerji M. et al., 2015,MNRAS,447,3368
       BASS (15,123): Swift-BAT AGN, Koss M. et al., 2017,ApJ,850,74
       BQLS (9,9): BOSS QSO lenses & pairs, More A. et al., 2016,MNRAS,456,1595
       C-COSM (180,180): Chandra COSMOS IDs, Marchesi S. et al., 2016,ApJ,817,34
       ChaMP (191,188): Trichas M. et al., 2012,ApJS,200,17
       Dart (24,24): Heavily Obscured QSOs, Hviding R. et al., 2017,arXiv:1711.01269
       DES (1,1): Dark Energy hi-z, Reed S.L. et al., 2015,MNRAS,454,3952
       DESQQ (21,21): STRIDES lenses, Anguita T. et al., 2018,arXiv:1805.12151
       DESQQ2 (12,12): STRIDES lenses, Treu T. et al., 2018,arXiv:1808.04838
       DPeake (7,3449): Double-peaked NELGs, Ge J.-Q. et al., 2012,ApJS,201,31
       DR12 (1627,5332): Alam S. et al., 2015,ApJS,219,12,
       DR12Q (233,414): SDSS-DR12Q, Paris I. et al., 2017,A&A,597,79
       DR14 (32895,40153): Abolfathi B. et al., 2018,ApJS,235,42,
             data at
       DR14Q (512696,525948): SDSS-DR14Q, Paris I. et al., 2018,A&A,613A,51,
             data at
       DR7 (6378,4870): SDSS DR7, Abazajian K.N. et al., 2009,ApJS,182,543,
             files at
       DR7Q (2128,340): SDSS Quasar DR7, Schneider D. et al., 2010,AJ,139,2360
       DUHIZ (2,2): DECaLS-UKIRT hi-z, Wang F. et al., 2017,ApJ,839,27
       eHAQ (82,81): Extended High AV, Krogager J.-K., 2016,ApJ,832,49
       ELQS-N (35,35): ELQS in NGC, Schindler J.-T. et al., 2018,arXiv:1806.03374
       GAIA2 (263,263): Gaia DR2, Gaia Collaboration et al., 2018,A&A,616A,1,
                    data as presented by SIMBAD,
       GArcs (3,3): SDSS Giant Arcs lens, Dahle H. et al., 2013,ApJ,773,146
       GL-DB (17,17): Gravitational Lens DB, Lemon. C., 2018 (provisional data)
       GLDD (1,1): Lensed QSO data-driven, Ostrovski F. et al., 2017,MNRAS,465,4325
       GLIKMAN (22,22): red WISE QSOs, Glikman E. et al., 2018,arXiv:1805.06961
       GLRED (1,1): lensed red QSO, Glikman E. et al.,2018,arXiv:1807.05434
       HAQ (2,2): High AV serendipitous, Heintz K.E. et al., 2016,AJ,152,13
       HAQC (1,1): High AV in COSMOS, Heintz K.E. et al., 2016,A&A,595,13
       HEINTZ (1,1): dusty absorbed QSO, Heintz K.E. et al., 2018,arXiv:1803.09805
       HIZ7.5 (1,1): QSO z=7.5, Bañados E. et al., 2018,Natur,553,473
       HMQ (28633,22891): Half Million Quasars catalog, Flesch E., 2015,PASA,32,10,
                          (see references therein to the original authors & papers)
       IGMCP (10,10): IGM close pairs, Rorai A. et al., 2017,Sci,356,418
       IMS (1,1): IR medium-deep hi-z, Kim Y. et al., 2015,ApJ,813,35
       IKEDA (1,1): Ikeda H. et al., 2017,ApJ,846,57
       LAMDR4 (7032,7032): LAMOST-DR4,
       LAMQ1 (716,652): LAMOST QUASAR DR1, Ai Y.L. et al., 2016,AJ,151,24
       LAMQ2 (3775,3664): LAMOST QUASAR DR2, Dong X.Y. et al., 2018,AJ,155,189
       LAMQ3 (3075,3075): LAMOST QUASAR DR3, Dong X.Y. et al., 2018,AJ,155,189
       LEMON (29,29): 24 Gaia lenses, Lemon C. et al., 2018,arXiv:1803.07601
       LEMON2 (26,26): 22 Gaia lenses, Lemon/Auger/McMahon, 2018,arXiv:1810.04480
       LIDMAN (1,1): SN Host Galaxy redshifts, Lidman C. et al., 2013,PASA,30,1
       LIRAS (168,158): LoCuSS IR AGNs, Xu, L. et al., 2015,ApJS,219,18
       LSSA (2,2): 2 lenses, Lucey/Schechter/Smith/Anguita, 2017,arXiv:1711.02674
       MALS-N (68,68): MEERKAT QSOs, Krogager J.-K. et al., 2018,arXiv:1802.00482
       MFJC (52,52): McGreer I.D., Fan X., Jiang L. & Cai Z.,2017,arXiv:1710.09390
       MORX (49082,0): Million Radio/X-ray Associations, Flesch E.,2016,PASA,33,52
       MQ (6731,619691): MILLIQUAS, original data in this catalog, Flesch E.,2018
       MZZ (9,9): Marano B., Zamorani G., Zitelli V., 1988,MNRAS,232,111
       NBCKDE (40937,40938): Richards G.T. et al., 2009,ApJS,180,67
       NBCKv3 (569752,569752): NBCKDE v3, Richards G.T. et al., 2015,ApJS,219,39
       OVRLAP (5,5): SDSS overlap hi-z QSOs, Jiang L. et al., 2015,AJ,149,188
       OzDES (664,638): Dark Energy SN QSOs, Tie S.S. et al., 2017,AJ,153,107
       P352-1 (1,1): P352-15, Baņados E. et al., 2018,arXiv:1807.02531
       PETERS (12942,12942): photo special, Peters C.M. et al., 2015,ApJ,811,95
       PGC (13559,8): Principal Galaxy Catalogue, Paturel G. et al.,2003,A&A,412,45
       PS1 (63,63): PAN-STARRS1 hi-z, Banados E. et al., 2016,ApJS,227,11
       PS1hiz (1,1): Tang, Ji-Jia et al., 2017,MNRAS,466,4568
       PS1MAZ (6,6): Mazzucchelli C. et al., 2017,arXiv:1710.01251
       PSO (3,3): PAN-STARRS z-dropouts, Venemans B.P. et al.,2015,ApJ,801L,11
       QPQ10 (70,70): Quasar pair DB, Findlay J.R. et al., 2018,arXiv:1804.08624
       RBS (3,3): Laporte N. et al., 2017,arXiv:1708.05173
       RLQ (4,3): Tuccillo D./Gonzalez-Serrano J.I./Benn C.R., 2015,MNRAS,449,2818
       RSG (1,1): Dorn-Wallenstein T.Z. & Levesque E., 2017,IAUS,329,376
       S82X (8,8): Red Quasars, LaMassa S.M. et al., 2017,arXiv:1709.01578
       SDSSHI (6,6): SDSS hi-z, Jiang L. et al., 2016,ApJ,833,222
       SFM201 (1,1): Schulze S. et al., 2012,A&A,546,20
       SHELLQ (33,33): Subaru hi-z, Matsuoka Y. et al., 2018,PASJ,70S,35
       SHELQS (30,30): SHELLQS hi-z, Yoshiki Matsuoka Y. et al., arXiv:1803.01861
       SMSSQ (2,2): SkyMapper hi-z, Zefeng Li Z. et al., 2018, arXiv:1805.03429
       SQLS (6,6): SDSS DR7 QSO Lens Search, Inada N. et al., 2012,AJ,143,119
       SUV (21,21): SDSS-ULAS/VHS QSOs, Yang J. et al., 2017,AJ,153,184
       SXDF (39,39): Subaru-XMMDF redshifts, Simpson C. et al., 2012,MNRAS,421,3060
       SXDS (309,308): Subaru-XMMDF spectra, Akiyama M. et al., 2015,PASJ,67,82
       ULTRA (1,1): Ultraluminous hi-z, Wu, X.-B. et al., 2015,Nature,518,512
       UVQS (433,517): UV QSOs, Monroe T.R. et al., 2016,AJ,152,25
       VAHIZ (2,2): VST ATLAS hi-z, Carnall A.C. et al., 2015,MNRAS,451,16
       VAHIZ2 (1,1): bright z>6 QSOs, Chehade B. et al., 2018,arXiv:1803.01424
       VAHIZ3 (1,1): VST-ATLAS lens, Schechter P.L. et al., 2018,arXiv:1805.01939
       VDES (8,8): VISTA Dark Energy Qsos, Reed S.L. et al., 2017,MNRAS,468,4702
       VIKING (4,4): VIKING IR, Venemans, G.A. et al., 2015,MNRAS,453,2259
       VIPERS (241,285): VIPERS PDR-2, Scodeggio M. et al., 2018,A&A,609A,84
       VMC (34,34): Magellanic IR QSOs, Ivanov V.D. et al., 2016,A&A,588,A93
       WARSAW (3,3): OGLE lens, Kostrzewa-Rutkowska Z. et al.,2018,arXiv:1801.08481
       WGD (2,2): DES/Gaia lenses; Agnello A. et al., 2017,arXiv:1711.03971
       WISEA (406757,0): AllWISE QSO candidates, Secrest N. et al.,2015,ApJS,221,12
       WISEHI (72,70): Hi-z QSOs from WISE, Wang F. et al., 2016,ApJ,819,24
       XDQSO (236744,0): SDSS-XDQSO, Bovy J. et al., 2011,ApJ,729,141
       XLSS (306,119): Stalin C.S. et al., 2010,MNRAS,401,294
       XMM2 (14,14): 2XMM-Newton cross-search, Combi J.A. et al., 2011,Ap&SS,331,53
       XMSS (182,150): Barcons X. et al., 2007,A&A,476,1191
       XWAS (490,449): Esquej P. et al., 2013,A&A,557,123
       YQLF (25,25): deep CFHT QSOs, Yang J. et al., 2018,arXiv:1801.01245
The citation for the classification (e.g., that the object is a quasar) can be from either the name or redshift citation.

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.).

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. Included candidates are those of 80%+ likelihood of being true quasars. For a known QSO (type = Q/A), Bl Lac type (type = B), or type-II (type = K/N), this field contains the percent chance that the shown radio/X-ray detection(s) is truly associated to it.

Candidates (objects without spectroscopic confirmation) consist of three separate classes of objects:

(1) Photometric quasars from the SDSS-based NBCKDE/NBCKDE-v3/XDQSO/Peters quasar candidate catalogs. Those catalogs give calculated QSO probabilities (pQSOs) for their objects which are not reported here; instead, the author has calibrated those pQSOs against SDSS-DR12Q classified objects to produce the QSO likelihoods given here. The calibration method is detailed in the author's HMQ paper (2015, PASA, 32, 10), appendix 1. Included candidates are those of 80%+ likelihood of being true quasars.

(2) WISE-sourced candidates are presented by their authors with a bulk pQSO as an average figure, with no individual pQSOs given. These I have generated by matching WISE candidates to optical objects (within a two arcsecond radius) and then dividing them into four-color (the colors being B-R, R-W1, W1-W2, and W2-W3) subsets which are then calibrated against SDSS-DR12Q classified objects to yield the pQSO for each subset.

(3) Radio/X-ray associated objects, totaling 55,816 without any other attribution. The likelihoods of these being true QSOs are calculated as described in the QORG paper (Flesch & Hardcastle, 2004, A&A, 427, 387).

71,105 photometric quasars are also radio/X-ray associated, and the displayed probability figure combines the photometric QSO likelihood P1 and the radio/X-ray derived QSO likelihood P2 as

       P = 1/(1+((1-P1)*(1-P2))/(P1*P2)).
Over all objects, using the probability as expected yield, the 1,941,558 type-I Milliquas objects will yield 1,886,706 actual type-I quasars/AGNs.

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,
       NVSS: NRAO VLA sky survey,
       SUMSS: Sydney U. Molonglo,
       MGPS: Molonglo galactic plane survey, same attribution as SUMSS

       ROSAT catalogs home page:
           - 1RXH: ROSAT HRI (high resolution imager)
           - 2RXP/2RXF: ROSAT PSPC (position sensitive proportional counter)
           - 1RXS: ROSAT RASS (all-sky survey, both bright & faint)
       2RXS: 2nd RASS source catalog, Boller Th. et al., 2016,A&A,588,103
       1WGA: White, Giommi & Angelini,
       CXO: Chandra Source Catalog v1.1,
       CXOG: Chandra ACIS source catalog, Wang S. et al., 2016,ApJS,224,40
       CXOX: XAssist Chandra source list,
       2XMM/2XMMi: XMM-Newton DR3,
       3XMM: XMM-Newton DR8,
       XMMSL: XMM-Newton Slew Survey v2.0, same attribution as 3XMM
       XMMX: XAssist XMM-Newton source list,
       1SXPS: Swift X-ray Point Source catalog,
Optical field solutions are calculated from the raw source positions of all these catalogs as described in the author's MORX paper (2016, PASA, 33, 52).

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.

Contact Person

Questions regarding the MILLIQUAS database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Friday, 19-Oct-2018 14:24:10 EDT