The U.S. Naval Observatory VLBI Spectroscopic Catalog
  Despite their importance for astrometry and navigation, the active galactic
nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF)
are relatively poorly understood, with key information such as their
spectroscopic redshifts, AGN spectral type, and emission/absorption line
properties generally missing from the literature. Using updated, publicly
available, state-of-the-art spectroscopic fitting code optimized for the
spectra of AGNs from low to high redshift, we present a catalog of emission
line and spectral continuum parameters for 1,014 unique ICRF3 objects with
single-fiber spectra from the Sloan Digital Sky Survey DR16. We additionally
present black hole virial mass scaling relationships that use H$\alpha$-,
H$\beta$-, Mg II-, and C IV-based line widths, all consistent with each other,
which can be used in studies of radio-loud objects across a wide range of
redshifts, and we use these scaling relationships to provide derived properties
such as black hole masses and bolometric luminosities for the catalog. We
briefly comment on these properties for the ICRF objects, as well as their
overall spectroscopic characteristics.
