The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
  We present the final Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog
from Data Release 16 of the extended Baryon Oscillation Spectroscopic Survey
(eBOSS). This catalog comprises the largest selection of spectroscopically
confirmed quasars to date. The full catalog includes two sub-catalogs: a
"superset" of all SDSS-IV/eBOSS objects targeted as quasars containing
1,440,615 observations and a quasar-only catalog containing 750,414 quasars,
including 225,082 new quasars appearing in an SDSS data release for the first
time, as well as known quasars from SDSS-I/II/III. We present automated
identification and redshift information for these quasars alongside data from
visual inspections for 320,161 spectra. The quasar-only catalog is estimated to
be 99.8% complete with 0.3% to 1.3% contamination. Automated and visual
inspection redshifts are supplemented by redshifts derived via principal
component analysis and emission lines. We include emission line redshifts for
H$\alpha$, H$\beta$, Mg II, C III], C IV, and Ly$\alpha$. Identification and
key characteristics generated by automated algorithms are presented for 99,856
Broad Absorption Line quasars and 35,686 Damped Lyman Alpha quasars. In
addition to SDSS photometric data, we also present multi-wavelength data for
quasars from GALEX, UKIDSS, WISE, FIRST, ROSAT/2RXS, XMM-Newton, and Gaia.
Calibrated digital optical spectra for these quasars can be obtained from the
SDSS Science Archive Server.
