MILLIQUAS ivo://nasa.heasarc/milliquas NASA/GSFC HEASARC Flesch 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source 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 eric@flesch.org. 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. This table was updated by the HEASARC in July 2023 based on a machine-readable catalog obtained from the author's MILLIQUAS website at <a href="https://quasars.org/milliquas.htm">https://quasars.org/milliquas.htm</a>. <p> 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. <p> 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. <a href="https://simbad.cds.unistra.fr/simbad">https://simbad.cds.unistra.fr/simbad</a> This is a service provided by NASA HEASARC . 2023OJAp....6E..49F https://heasarc.gsfc.nasa.gov/W3Browse/all/milliquas.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=milliquas& GET text/xml 180 99999 true 335.7540586 -89.3858719 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=milliquas GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_milliquas&Action=More+Options&Action=Parameter+Search&ConeAdd=1 GALAXY CATALOG 0.0166666666666667 Optical public milliquas Million Quasars Catalog (MILLIQUAS), Version 8 (2 August 2023) name Source Identification from the Literature meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable broad_type Broad Classification of Object src.class char nullable rmag Red Optical Magnitude mag phot.mag;em.opt.R double nullable bmag Blue Optical Magnitude mag phot.mag;em.opt.B double nullable redshift Redshift from the Literature or Estimated src.redshift double nullable radio_name Radio Identification, If Any meta.id.assoc;em.radio char nullable xray_name X-Ray Identification, If Any, But Can Be Radio Lobe If Radio Source meta.id.assoc;em.X-ray char nullable ref_name Reference Code for the Source Identification from the Literature meta.ref;src char nullable blue_psf_flag Flag Indicates Blue Optical PSF Class meta.code;instr.det.psf char nullable alt_name_2 Additional Radio Lobe Identification or Additional Radio or X-Ray Identification meta.id.assoc;em.radio char nullable class Browse Object Classification src.class short nullable red_psf_flag Flag Indicates Red Optical PSF Class meta.code;instr.det.psf char nullable lii Galactic Longitude degree pos.galactic.lon double nullable optical_flag Flags Indicate Comments on Optical Object meta.code;em.opt char nullable bii Galactic Latitude degree pos.galactic.lat double nullable ref_redshift Reference Code for the Redshift from the Literature meta.ref;src.redshift char nullable alt_name_1 Radio Lobe Identification or Additional Radio or X-Ray Identification meta.id.assoc;em.radio char nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable