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MILLIQUAS - Million Quasars Catalog, Version 8 (2 August 2023)



This table contains the Million Quasars (MILLIQUAS) Catalog, Version 8 (2 August 2023). It is a compendium of 907,144 type-I QSOs and AGN, largely complete from the literature to 30 June 2023. 66,026 QSO candidates are also included, calculated via radio/X-ray association (including double radio lobes) as being 99% likely to be quasars. Blazars and type-II objects are also included, bringing the total count to 1,021,800. 60.7% of all objects show Gaia-EDR3 astrometry.

Low-confidence/quality or questionable objects (so deemed by their researchers) are not included in Milliquas. Additional quality cuts can be applied as detailed in the HMQ paper (Flesch 2015,PASA,32,10). Full QSO/AGN classification is accomplished via spectral lines, yielding a reliable spectroscopic redshift. Two spectral lines are required, or one spectral line refining a compatible photometric redshift. Obscured AGN with redshifts from the hosts only are taken to be type-II objects. Some legacy quasars with neither good spectra nor radio/X-ray association were flagged by Gaia-EDR3 as 5-sigma moving (i.e., stars), and so were removed from Milliquas. All objects are de-duplicated across source catalogs. The author's aim here is to present one unique reliable object per each data row. Two NIQs offset < 2 arcsec can be reported as a single object if within the same host. Lenses are reported as single objects onto the brightest quasar imaged. (Milliquas is not a catalog of lenses.)

The contents are relatively simple; each object is shown as one entry with the sky coordinates (of whatever epoch), 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 confirmed quasars of this catalog (to Jan 2015) were published as the Half Million Quasars (HMQ) catalog: Flesch E., 2015,PASA,32,10. Note however that Milliquas uses optical sky data from ASP (2017,PASA,34,25) whereas the HMQ used optical sky data from QORG (2004,A&A,427,387) Appendix A.

Catalog Bibcode



Flesch, E.W.
    The Million Quasars (MILLIQUAS) Catalog, Version 8 (2 August 2023)
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 July 2023 based on a machine-readable catalog obtained from the author's MILLIQUAS website at

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 and CDS cross-match service (to obtain Gaia-EDR3 and Pan-STARRS photometry) provided by 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 catalogs 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 arcsecond 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   Quasars from individual papers from August 2017 forward to
                   15 October 2018 have been added, plus some from a couple
                   older papers. Quasar doublets are more carefully processed
                   to show 2 quasars instead of 1. A few gravitationally
                   lensed images are added as type='L', in addition to the
                   already-catalogued brightest one. These are added only
                   where the optical data shows them in order to account for
                   any radio/X-ray associations to them. The 3XMM-DR8 X-ray
                   source catalog has been added and new X-ray associations
                   calculated. A bug in v5.3 dropped radio/X-ray associations
                   to some high-z quasars was fixed.
     5.5  19Nov18  Quasars from publications to 14 November 2018 were added.
                   The SDSS data were reprocessed to ensure DR14 data is used
                   where available. Close quasar pairs and lens images
                   processing was completed. 631 "unknown class" (type=U)
                   objects (SDSS pipeline QSOs without subclass) were added.
                   There are not usually accepted into Milliquas but they had
                   probable radio/X-ray associations of p>80% which thus
                   qualify them for inclusion. The SDSS pipeline redshift for
                   these were included provisionally. The J2000 decimal
                   round-up was increased to avert truncation.
     5.6  17Dec18  Quasars from publications to 15 December 2018 were added.
                   The 3rd release of SDSS-DR14Q (v4.4) was incorporated,
                   adding ~300 quasars which had no astrometry in their
                   earlier releases. All SDSS data was reprocessed to get rid
                   of artifacts which had crept in. In preparation for LAMOST
                   DR5Q (Yao et al 2018,arXiv:1811.01570), the LAMOST DR4
                   auto-quasars were demoted to quasar-candidates. LAMOST
                   pipeline quasars were processed using the same rules as
                   with SDSS pipeline. Removed 223 objects from
                   Iovino/Clowes/Shaver,1996,A&AS,119,265 which had no quasar
                   profile nor radio/X-ray/WISE associations, leaving 917 in
                   Milliquas, resolving the cautionary note from
                   HMQ (2015,PASA,32,10) section 2.B.4 end.
     5.7  07Jan19  Quasars were added from publications to 7 January 2019,
                   including LAMOST QSO DR5. The logic was tightened up for
                   using SDSS SUBCLASS and ZWARNING fields to decide
                   classifications for SDSS objects, including pipeline-only
                   candidates. Milliquas was previously classifying all
                   QSOs/AGN of z<0.1 as AGN. This boundary was moved to
                   z=0.05 because of many core-dominated QSOs between z=0.05
                   and 0.1, e.g., IRAS 01267-2157 (SDSS J012910.99-214156.8)
                   at z=0.93. HMQ (2015,PASA,32,10), section 5, discusses
                   these luminosity-based boundaries. 22 objects from Boyle
                   et al., 1990,MNRAS,243,18, classified by them as "possible"
                   QSOs with "uncertain" redshifts, were removed from
                   Milliquas. Positional fixes were done on ~90 legacy
                   objects, mostly moves of <5 arcsec.
     6.0  15Mar19  Quasars were added from publications to 15 March 2019.
                   For ease of use, the "HMQ" citation (necessitating
                   consultation of the HMQ catalog 2015-PASA-32-10 to
                   identify the discovery article) was replaced by the
                   HMQ-given 4-digit citation number. 30512 entries were
                   changed, and the HMQ references file can be directly
                   consulted for any numeric citation, making Milliquas into
                   a stand-alone catalog. Positional fixes were made to 9
                   legacy objects. Where SDSS had a different redshift for a
                   LAMOST-discovered quasar, if the difference is >0.1z, the
                   name and discovery credit were transferred to SDSS. This
                   was done for 6 objects. 42 AGN are dropped because their
                   discovery paper Mauch & Sadler 2007,MNRAS,375,931 flagged
                   those classifications as "not certain" and they had
                   neither stellar psfs nor secure (80%+) radio/X-ray
                   associations. The unseen Soviet BAL quasar "SBS 1401+566"
                   was dropped. The quasar "Q 1409+732" was moved to the
                   coordinates stated by its discovery paper Anderson &
                   Margon 1987,Nature,327,125, where a suitable object
                   resides. Confusion came from that paper's discrepant
                   finding chart onto a plate flaw.
     6.1  12May19  Quasars were added from publications to 12 May 2019.
                   Gaia-DR2 astrometry was used and flagged for 63% of
                   Milliquas (MQ) objects. Gaia sources were matched 1-to-1
                   with MQ objects on the criterion that the Gaia source is
                   that nearest to the MQ object and that the MQ object is
                   that nearest optical (out of a 1.163G optical DB) to the
                   Gaia source. Care was taken to avoid false matches. 99%
                   of all matches are within an arcsec offset, but to find
                   valid farther matches, all matches were binned by object
                   class and offset distance in 0.1 arcsec bins, with
                   hundreds of targeted spot checks done to refine offset
                   limits and to check objects with anomalous Gaia BP-RP
                   color suggestive of a false match. SDSS quasar candidates
                   could not be matched beyond 1 arcsec offset because they
                   are often optically faint and/or in close groups for which
                   Gaia had a different object only. AGN cores match to 1.5
                   arcsec beyond which Gaia often shows nearby stars only.
                   QSOs/Bl-Lacs match well out to within 4 arcsec; for these
                   I spot-checked all matches beyond 2 arcsec and all with
                   off-colors beyond 1 arcsec offset and removed 14 false
                   matches. However, for Gaia sources without BP and RP
                   colors, QSOs match reliably only within 2 arcsec and
                   Bl-Lacs within 1.5 arcsec. X-ray/radio-only candidates
                   (unique to MQ) match reliably out to within 2.5 arcsec
                   offset. In all cases it was paramount to avoid false
                   matches, thus very many true matches were lost beyond
                   the offset cutoffs. Reclassifications were done for
                   Milliquas objects deemed by the SDSS-DR14 pipeline to be
                   plain galaxies -- these were heavily spot-checked to
                   confirm. 16 QSOs, 172 AGN and 2343 type-II objects were
                   found to be just galaxies and so are dropped, and 433
                   host-dominated QSOs were reclassified to AGN.
     6.2  22May19  About 50 fixes were done on Gaia-DR2 opticals selected in
                   crowded places. Quasars were added from publications to 22
                   May 2019, including the PS-ELQS. 3LAC was reprocessed to
                   fix a few selections and improve completeness. The z=2.136
                   QSO "SDSS J101012.77+560520.0", overlooked by SDSS, was
     6.3  16Jun19  Quasars were added from publications to 15 June 2019,
                   including 4LAC. 3,581 galaxies with double radio lobes
                   were added as type=G because the lobes show that they have
                   active nuclei of some kind, even if well hidden.
                   Positional fixes of a few arcsec were done for ~50 legacy
                   objects. Blazar candidates with neither redshift nor
                   radio/X-ray association, about 30 objects, were dropped.
                   Most were stated to be low confidence in legacy papers.
     6.4  11Dec19  Quasars were added from publications to 11 December 2019.
                   The SDSS-DR16 pipeline release was added. The author
                   processed it using the standard HMQ rules which yield QSO
                   classifications that accord well to the follow-up manual
                   SDSS classifications. A new rule for Milliquas
                   classification was added such that STARFORMING and
                   STARBURST subclasses, or GALAXY classification by the
                   DR12Q superset, are now taken to indicate optical host
                   domination, e.g., classed as AGN instead of QSO. More
                   candidates with double radio lobes were added, active
                   nuclei being indicated. A photometric threshold guards
                   against starforming interlopers. The pQSOs of SDSS
                   candidates which are eBOSS targets were lowered due to
                   anti-selection, i.e., possibly DR16Q-classified as a
                   non-quasar. Candidates which consequently fell below
                   pQSO=80% (~57K) were dropped. The Chandra Source Catalog
                   v2 was added, but only as a supplement to the CSC v1.1
                   because v2 provides only stacked data for which the
                   optical solution used by Milliquas cannot be calculated.
     6.4b 19Dec19  Some extra processing of the new SDSS-DR16 data yielded 534
                   more type-I objects and fixed the astrometry of 381
                   objects which had been offset by up to 3 arcseconds. About
                   800 QSOs were flagged as host-dominated and so were
                   reclassified to AGN.
     6.4c 31Dec19  Quasars were added from publications to 31 December 2019.
                   The 4XMM-DR9 XMM-Newton catalog was added and X-ray
                   associations calculated, replacing 3XMM-DR8. The 2SXPS
                   Swift XRT catalog was added and X-ray associations
                   calculated, replacing 1SXPS. Gaia astrometry was removed
                   from 18 quasars and 66 candidates which were in doublets
                   (on the sky) for which Gaia had astrometry only for the
                   other object. SDSS-DR16 redshifts more fully replaced
                   earlier SDSS pipeline data.
     6.5  14Jun20  Quasars were added from publications to 14 June 2020.
                   Gaia-sourced parallaxes and proper motions were analyzed
                   to see if they could identify false quasars. Legacy quasar
                   publications were then group tested such that those with a
                   high flag rate (>20% compared with 2% overall, signaling
                   the presence of low-quality data) had their flagged
                   objects dropped, provided, as a confirmation, that those
                   objects also had no radio/X-ray associations. The counts
                   of dropped objects were:
                     -- 28 out of 40 (70%) from Zhan & Chen, 1987 & 1989 ChA&A
                     -- 400 out of 916 (44%) from Iovino/Clowes/Shaver,
                     -- 50 out of 194 (26%) from Savage/Trew/Chen/Weston,
                     -- 111 out of 517 (21%) from Drinkwater 1987.
                   In total, 589 "quasars" were dropped for having
                   parallaxes/proper motions. 136 SDSS-DR14 objects which
                   were dropped by SDSS-DR16 were removed. About 1500 objects
                   had their photometry supplemented from Pan-STARRS data.
     6.6  30Aug20  Quasars were added from publications to 30 August 2020.
                   The SDSS-DR16Q data (Lyke+ 2020) were incorporated.
                   Combined with the DR16 pipeline data, these contributed
                   ~200K new quasars beyond DR14 plus many valuable
                   reclassifications of the SDSS-IV data. In processing this
                   vast data pool, the author identified 37 new quasars not
                   classified by DR16/DR16Q. These were added in Milliquas
                   with ref_name="MQ" and ref_redshift="DR16QN"/"DR16". Data
                   selection of DR16 pipeline data was by HMQ (Flesch 2015)
                   rules, including choice of spectra. Data flagged with
                   ZWARNING=256 (bad astrometry) were validated by testing
                   and are included. Details of usage of the SDSS-DR16/DR16Q
                   data will be included in a Milliquas paper in preparation
                   (Flesch 2021).
     7.0  30Sep20  Quasars were added from publications to 30 September 2020.
                   SDSS-DR16 represented the conclusion of the eBOSS and BOSS
                   quasar surveys, and that conclusion somewhat orphaned the
                   leftover candidates from the SDSS-based photometric
                   catalogs. Said candidates without any radio/X-ray/WISE
                   associations were unlikely to be targeted in this decade,
                   and so were dropped from Milliquas, 574,538 of them. Said
                   candidates which did have WISE associations, numbering
                   35,086, were changed to display AllWISE names. These
                   significant changes prompted this release to be numbered
                   v7.0.Clean-ups were done on the uptake of SDSS-DR16Q/DR16
                   by Milliquas v6.6, notably 4,506 DR16Q quasars previous
                   presented as candidates, were designated to be QSOs. Also,
                   404 low-quality pipeline objects which were presented as
                   QSOs were dropped. WISEA photometric redshifts were
                   recalculated using the DR16-augmented training set, and
                   Pan-STARRS-based photometric redshifts were calculated for
                   radio/X-ray associated candidates on the PS1 footprint
                   (all-sky N of decl. S30) using the four-color method of
                   2015,PASA,32,10, Appendix 2. 222 candidates in a solid
                   degree centered on J2033+412 in Cygnus were dropped. They
                   are obvious stars, albeit near to background Galactic
                   X-ray sources.
     7.1  14Feb21  Quasars were added from publications to 14 February 2021.
                   For quasar candidates, the pQSO (likelihood that the
                   candidate is a quasar) threshold for inclusion into
                   Milliquas was lowered to 60%. This was done to present
                   more radio/X-ray associated candidates which were not
                   available elsewhere. Audits on the inclusion of DR16Q into
                   Milliquas led to tweaks of the selection of DR16Q objects.
                   Other SDSS data were also audited. Also, all galaxy data
                   are removed in order to focus exclusively on quasars.
                   LAMOST-DR6 was added -- being pipeline-only data, its
                   quasar classifications were accepted into Milliquas only
                   when supported by radio/X-ray/WISEA pQSOs. 4XMM-DR10 X-ray
                   sources were added, replacing DR9.
     7.2  02May21  Quasars were added from publications to 30 April 2021.
                   The VLASS Quick Look radio catalog was included, which
                   added 34189 new radio core associations and 6793 probable
                   double radio lobe associations. Ongoing audits of SDSS and
                   LAMOST quasars resulted in a few additions and drops. Some
                   WISEA-supported SDSS/LAMOST pipeline quasars were accepted
                   which were otherwise marginal. Also, some likely galaxies
                   were removed.
     7.3  31Oct21  Quasars were added from publications to 31 October 2021.
                   17 classified quasars were dropped as moving stars
                   (Gaia-DR2 flagged and confirmed on legacy DSS charts), 4
                   as galaxies, and 1 line poacher. 42,637 quasar candidates
                   for which Gaia-DR2 shows proper motion or parallax, have
                   been dropped for efficiency. 1365 quasars and ~100K
                   candidates without Gaia-DR2 J2000 were reconciled to
                   Pan-STARRS or SDSS J2000 with an average positional shift
                   of ~0.1 arcsec. About 400 very faint (r>22) legacy quasars
                   were positionally tweaked by comparing to DES and
                   Pan-STARRS images, usually ~1 arcsec, some more. Selection
                   and processing tweaks done on candidates, adding a net 93.
                   AGES (Kochanek+ 2012) was reloaded using the CDWFS X-ray
                   survey (Masini+ 2020,ApJS,251,2) to support object
                   selection. AGES did not publish their spectra; 368 of
                   their objects were switched to cite DR16Q which shows
                   spectra. RACS (Hale+ 2021, arXiv:2109.00956) radio
                   associations were added. RASS (ROSAT All-Sky Survey) X-ray
                   data was dropped, as it has become clear over time that
                   its resolution is too coarse to confidently identify
                   sources. OzDES1 (Tie+ 2017,AJ,153,107) were fully replaced
                   by OzDES2. 4XMM-DR11 X-ray sources were added, replacing
     7.4  12Dec21  Quasars were added from publications to 12 December 2021.
                   SDSS-DR17 was processed, with 1003 new quasars and 266 new
                   MaNGA AGN added. The eFEDS AGN catalog was processed, with
                   532 new quasars added. Only the best-quality data were
                   used (5029#); of which, 1139 were new objects.
                   Redshift/photometry cut-offs were used on those to avoid
                   galaxy contamination. WISEA-only candidates were removed
                   to avoid repeating candidates from other catalogs, which
                   resulted in 448,009 candidates removed. The only
                   candidates presented are those with radio/X-ray
                   associations calculated by this work. More Pan-STARRS
                   astrometry was added. 1219 RACS associations with bad RACS
                   names (wrong hemisphere) were fixed.
     7.5  30Apr22  Quasars were added from publications to 30 April 2022.
                   The LAMOST DR7 pipeline added 646 QSOs supported by
                   radio/X-ray/WISEA association. A search revealed six
                   earlier (2011-2021) papers missed due to not being on
                   ArXiv, paywalled data, or otherwise overlooked. The were
                   added (yielding 156 new objects) and indexed below as
                   AT20G, ICRFz, GB6hiz, Hdots1, Hdots2, and 4FGL3.
                   Candidates selection was tweaked for efficiency with a net
                   total of ~800 fewer objects. The citations 2MAGN
                   (Zaw+,2019) and 6dAGN (Chen+,2022) classify faint nuclear
                   emission. Their type-I & Kewley-criterion type-II objects
                   were accepted into the catalog. HETDEX AGN of 2+ spectral
                   lines were added into Milliquas after deduplication.
     7.6  15Sep22  Quasars were added from publications to 31 August 2022.
                   All objects/candidates calculated as having 80-100%
                   likelihood of radio/X-ray association (RXpct) were
                   included, including classified galaxies. This increased
                   the Milliquas row count by ~50%. The threshold was
                   increased to 80% to increase reliability. RXpct and Qpct
                   (pQSO) were split into separate columns clarify the
                   distinction for users. Gaia-DR3 QSO candidates (indexed as
                   "GAIA3" below) with redshifts were matched to radio/X-ray
                   detections, and those with calculated associations of 80%+
                   likelihood were added as candidates. Their redshifts were
                   rounded to 0.1z to show that they are only approximate;
                   because of the lack of spectral redshift, they could not
                   be fully classified as QSOs in Milliquas. The
                   classification of "q" (quasar candidate) was added to
                   denote candidates which are 99% likely to be true QSOs, as
                   per the method of Flesch 2015,PASA,32,10 Section 8.
                   4XMM-DR12 X-ray sources were added, replacing DR11.
                   MIGHTEE spectral AGN (indexed as "MIGHTE" below) were
                   added, but with cuts to avoid galaxy contamination: 2/5
                   MIGHTEE "True" tests required, and z>0.7.
     7.7  15Oct22  Quasars were added from publications to 15 October 2022.
                   Some quasar candidates of pQSO 60%-79% were missing; now
                   added. Positional fixes done on ~6000 candidates which had
                   "epoch 2000" astrometry from USNO-B. Where USNO-B adjudged
                   the object to be moving, the epoch 2000 projection could
                   be discrepant by many arcsec. Pan-STARRS astrometry has
                   been obtained for these objects where available, i.e.,
                   those of decl>-30. Those remaining have been flagged as
                   questionably located.
     7.8  04Dec22  Quasars were added from publications to 4 December 2022.
                   LoTSS (2022,A&A,659,A1) radio associations were included,
                   adding about 272K candidates. VLASS was reprocessed to
                   include only Gaussian detections, and more of them. This
                   added a net 14,734 more quasar candidates. Association
                   likelihoods were calculated in 0.1-arcsec offset bins for
                   all radio/X-ray input surveys. Galaxies and low-likelihood
                   QSO candidates were removed.
     7.9  05Feb23  Quasars were added from publications to 5 February 2023,
                   including SDSS-DR18 and LAMOST QSO DR6-DR9. Gaia-EDR3
                   proper motion data were used to select objects to audit,
                   especially those of unclear classification from legacy
                   surveys. The net outcome was the addition of ~500 quasars,
                   mostly from LAMOST QSO DR1-DR5. Also notable were 12 (out
                   of 91) Hazard objects dropped due to proper motion
                   detected, and with no redshift confirmation from SDSS nor
                   radio/X-ray. DES DR2 astrometry and/or photometry were
                   supplied to ~15K objects.
     7.10 15Apr23  Quasars were added from publications to 15 April 2023.
                   Gaia-DR3 quasar candidates' redshifts are henceforth
                   rounded to the 0.01z instead of 0.1z because their
                   performance is being seen (by the astronomical community)
                   to be that good. The method of Cristiani+ 2023
                   (cite='QUBzs') approaches full spectroscopy and was used
                   to classify selected Gaia-DR3 candidates as quasars. That
                   subset of their output which show radio/X-ray association
                   were accepted as quasars in this version. ~15,000
                   candidates with only single-band photometry and only one
                   radio/X-ray detection were dropped because ~half of those
                   are not optically seen at all.
     7.11 30Jun23 Quasars were added from publications to 30 June 2023. The
                   DESI-EDR was included, adding 60,488 new quasars. Quality
                   checks resulted in the removal of about 2000 poor-spectrum
                   objects and duplicates. This selection anticipated that of
                   the upcoming DESI-EDR Quasar VAC. With the Milliquas
                   project drawing to a close after 15 years of publications.
                   30-June-2023 is the date of "closing the books". Thus,
                   this version (7.11), much like the final Milliquas (v8) to
                   come, adhered to the selection rules of the Half-Million
                   Quasars catalogue (HMQ: 2015,PASA,32,10), which selected
                   classified quasars and candidates of 99% pQSO.
                   Accordingly, v7.11 also restricted to this selection, and
                   so reduced the catalog to just over a million objects.
                   Candidates of lesser pQSO are still available from the
                   MORX catalogue. Citations were
                   provided in a single file, milliquas-references.txt.
     8    22Jul23  Final version. About ~600 more DESI-EDR quasars were added
                   via further processing and visual inspections of spectra.
                   Two columns were removed, the radio/X-ray detection
                   likelihood and the QSO likelihood, since all objects now
                   are of pQSO >= 99%. 4XMM-DR13 X-ray sources were added,
                   replacing DR12. LSXPS X-ray data were updated through


The designation of the source as taken from the literature. Nameless radio/X-ray associated objects here utilize 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 J000001.89+443053.8.

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. That accommodates a minuscule round-up to avoid truncation, such as when converting to sexagesimal, for example. 60.7% of the entries have Gaia astrometry, 27.8% have SDSS astrometry, and 8.3% have Pan-STARRS astrometry.

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. That accommodates a minuscule round-up to avoid truncation, such as when converting to sexagesimal, for example. 60.7% of the entries have Gaia astrometry, 27.8% have SDSS astrometry, and 8.3% have Pan-STARRS astrometry.

The Galactic Longitude of the quasar candidate. This parameter has been added by the HEASARC and is converted from the provided equatorial position.

The Galactic Latitude of the quasar candidate. This parameter has been added by the HEASARC and is converted from the provided equatorial position.

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

       Q = QSO, type-I broad-line core-dominated, 860100 of these.
       A = AGN, type-I Seyferts/host-dominated, 47044 of these.
       B = BL Lac type object, 2814 of these.  (FSRQs are typed as QSOs here)
       K = NLQSO, type-II narrow-line core-dominated, 6048 of these.
       N = NLAGN, type-II Seyferts/host-dominated, 39768 of these.  Incomplete,
           and includes an unquantified residue of legacy NELGs/ELGs/LINERs,
           plus some unclear AGN.  This is the catch-all category.
       S = star classified but showing quasar-like photometry and radio/X-ray
           association, thus included as a quasar candidate; 124 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. 97% of the optical photometry are from the ASP (2017,PASA,34,25) which presents data from the APM (, USNO-A and USNO-B (, and the SDSS ( Optically faint photometry is supplemented from Pan-STARRS ( and DESI data. APM/USNO-B galaxies brighter than 17th magnitude are usually represented as far too bright due to PSF modeling. Integer magnitudes (e.g., 22.00) are estimates if both bands are integers or one band is 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. 97% of the optical photometry are from the ASP (2017,PASA,34,25) which presents data from the APM (, USNO-A and USNO-B (, and the SDSS ( Optically faint photometry is supplemented from Pan-STARRS ( and DESI data. APM/USNO-B galaxies brighter than 17th magnitude are usually represented as far too bright due to PSF modeling. Integer magnitudes (e.g., 22.00) are estimates if both bands are integers or one band is 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.

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 those plates
           were always taken on the same night, thus the red-blue color is
           correct even for variable objects. The epochs for these are 1950s.
       j = optical magnitudes are SERC J (Bj 4850A) and R (red 6400A) from the
           POSS-II or UKST surveys.  Red-blue color is less reliable because the
           red and blue plates were taken in different epochs, i.e., years apart.
       b = blue magnitude is Vega 4400A (Johnson), red is 6400A (Cousins).
       g = blue magnitude is SDSS-type green 4900A, red is r 6200A.  Also denotes
           SDSS astrometry if not otherwise flagged.
       n = blue magnitude is Pan-STARRS green 4900A, red is r 6200A. Also denotes
           Pan-STARRS astrometry if not otherwise flagged.
       d = magnitudes are DES DR2 AB r & g.  Also denotes DESI astrometry if not
           otherwise flagged.
       u = blue magnitude is SDSS ultraviolet 3850A.
       v = red magnitude is visual 5500A, or estimated from a sky chart/viewer.
       i = red magnitude is infrared 7500A.
       z = red magnitude is infrared z 8600A.
       r = red magnitude is r 6200A.
       (blank) = red alone is 6400A (Cousins); if both magnitudes are present,
           then estimates.
       G = Gaia-EDR3 astrometry shown, precessed to J2000 by CDS.  If 'G' is alone
           then the magnitudes are Gaia RP & BP, or Gaia G if red band only.
       N = Pan-STARRS astrometry shown.  If 'N' is alone, PS photometry also.
       D = DES DR2 astrometry shown.  If 'D' is alone, DES photometry also.
       + = variability nominally detected in both red/blue over multi-epoch data.
       m = proper motion detected.  If from Gaia-DR2/3 ('G' also present in this
           field), then this is proper motion or parallax which usually signifies
           a star, but optical centroids can deflect within the optical gradient
           of a near moving neighbor or if either object is variable; some will
           be quasars.  If not Gaia, it is from USNO-B which is nominal only.
       e = USNO-B1.0 "epoch 2000" projected location based on nominal proper
           motion, can miss true location by many arcsec.
       % = swap of two "unplugged" SDSS spectra which crossed wires (7 of these).
       a = object is host-dominated with faint nuclear activity, such as an SDSS
           pipeline galaxy with an AGN subclass or AGN-classed elsewhere, see
           its citation.  Milliquas class is 'A' if BROADLINE, else 'N'. (See

A coded representation for the point spread function (PSF) of the optical source in the red. The APM, USNO-B, SDSS, and Pan-STARRS 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 = unseen / unclear in this band (fainter than plate depth, confused, etc.)

A coded representation for the point spread function (PSF) of the optical source in the blue. The APM, USNO-B, SDSS, and Pan-STARRS 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 = unseen / unclear in this band (fainter than plate depth, confused, etc.)

The redshift of the object, taken from the literature as specified in the ref_redshift parameter. Spectroscopic/grism redshifts are required for objects classified as Q/A/K/N and is optional for B (BL Lac type). Photometric redshifts are rounded to 0.1z (and can be identified by that rounding) and are either taken from the cited catalog or calculated here using the four-color method of Flesch 2015,PASA,32,10, Appendix 2, using 4 colors from SDSS ugriz, Pan-STARRS grizy (or ogriz with calibrated POSS-I O), or WISEA colors B-R, R-W1, W1-W2, and W2-W3. Photometric redshifts apply onto a quasar template mostly and not so well to galaxies. GAIA3 candidates show the "QSOC" estimated redshift provided by Gaia-DR3, rounded here to 0.01z.

A character code for the literature reference from which the name was taken. The meaning of these character codes can be found at The citation for the classification (e.g., that the object is a quasar) can be from either the name or the 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.).

The identification of the best core radio detection associated with the quasar candidate, if any.

This is the identification of the best X-ray detection (i.e., the highest probability 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,
       VLA (abbrev. of VLASS1QLCIR): VLASS Quick Look,
       RACS: Rapid ASKAP Continuum,, source file
       RACD: RACS as above, but from their main detection ("Gaussian") file
       ILT:  LoTSS-DR2,, main source catalog
       ILD:  LoTSS-DR2 as above, but from their main detection ("Gaussian") file
       NVSS: NRAO VLA sky survey,
       SUMSS: Sydney U. Molonglo,
       MGPS: Molonglo galactic plane,
       1RXH: ROSAT HRI (high resolution),
       2RXP: ROSAT PSPC (proportional),
       1WGA: White, Giommi & Angelini,
       CXOG: Chandra ACIS source catalog, Wang S. et al., 2016,ApJS,224,40
       CXO:  Chandra Source Catalog v1.1,
       2CXO: Chandra Source Catalog v2.0,
       CXOX: XAssist Chandra,
       2XMM/2XMMi: XMM-Newton DR3,
       4XMM: XMM-Newton DR13,
       XMMSL: XMM-Newton Slew Survey Release 2.0, same attribution as 4XMM
       XMMX: XAssist XMM-Newton,
       LSXPS: Swift X-ray Point Sources, (01July23)
RASS (ROSAT All-Sky Survey) is not included as its low resolution is not usable in isolation. Optical field solutions are calculated from the raw source positions of all these catalogs (except 2CXO) as described in the author's MORX paper (2016,PASA,33,52).

The identification of the radio lobe (as indicated by a "2" in the broad_type parameter) or an additional radio or X-ray identification associated with the quasar candidate, if any.

An additional identification of the radio lobe (as indicated by a "2" in the broad_type parameter) 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 Help Desk.
Page Author: Browse Software Development Team
Last Modified: Friday, 16-Feb-2024 16:59:32 EST