VizieR Online Data Catalog: The Million Quasars (Milliquas) catalogue, version 8 (Flesch, 2023)

This is a compendium of 907144 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 1021800. 60.7% of all objects show Gaia-EDR3 astrometry.

Citations are provided in a single file, refs.dat.

Low-confidence/quality or questionable objects (so deemed by their researchers) are not included in Milliquas. Additional quality cuts can apply as detailed in the HMQ paper (Flesch, 2015PASA...32...10F). Full QSO/AGN classification is 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 redshift from the host only, are taken to be type-II objects. Some legacy quasars with no good spectra nor radio/X-ray association were flagged by Gaia-EDR3 as 5-sigma moving (i.e., stars), and so removed from Milliquas. All objects are de-duplicated across source catalogues. The 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 image; Milliquas is not a catalogue of lenses.

The catalog format is simple, each object is shown as one line bearing the J2000 coordinates (of whatever epoch), its original name, object class, red and blue optical magnitudes, PSF class, redshift, the citations for the name and redshift, plus up to four radio/X-ray identifiers where applicable.

Please cite as Milliquas v8, Flesch, E.W. 2023, paper in preparation. Questions/comments/praise/complaints may be directed to me at eric(at)flesch.org.

(3 data files).