Yue Shen1,2
Abstract.
I review the current status of quasar black hole (BH) mass
estimations. Spectroscopic methods have been developed to estimate
BH mass in broad line quasars to an accuracy of ~0.5 dex.
Despite their popularity, significant issues and confusion remain
regarding these mass estimators. I provide an in-depth discussion on
the merits and caveats of the single-epoch (SE) virial BH mass
estimators, and a detailed derivation of the statistical biases of
these SE mass estimates resulting from their errors. I show that
error-induced sample biases on the order of a factor of several are
likely present in the SE mass estimates for flux-limited,
statistical quasar samples, and the distribution of SE masses in
finite luminosity bins can be narrower than the nominal uncertainty
of these mass estimates. I then discuss the latest applications of
SE virial masses in quasar studies, including the early growth of
supermassive black holes, quasar demography in the mass-luminosity
plane, and the evolution of the BH-host scaling relations, with
specific emphases on selection effects and sample biases in the SE
masses. I conclude that there is a pressing need to understand and
deal with the errors in these BH mass estimates, and to improve
these BH weighing methods with substantially more and better
reverberation mapping data
Keywords: black hole physics -- galaxies: active -- quasars: general -- surveys
1Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101, USA
2Hubble Fellow