Orientation and quasar black hole mass estimation
  We have constructed a sample of 386 radio-loud quasars with z < 0.75 from the
Sloan Digital Sky Survey in order to investigate orientation effects on black
hole mass estimates. Orientation is estimated using radio core dominance
measurements based on FIRST survey maps. Black hole masses are estimated from
virial-based scaling relationships using H-beta, and compared to the stellar
velocity dispersion (sigma_*), predicted using the Full Width at Half Maximum
(FWHM) of [O III] 5007, which tracks mass via the M-sigma_* relation. We find
that the FWHM of Hbeta correlates significantly with radio core dominance and
biases black hole mass determinations that use it, but that this is not the
case for sigma_* based on [O III] 5007. The ratio of black hole masses
predicted using orientation-biased and unbiased estimates, which can be
determined for radio-quiet as well as radio-loud quasars, is significantly
correlated with radio core dominance. Although there is significant scatter,
this mass ratio calculated in this way may in fact serve as an orientation
estimator. We additionally note the existence of a small population radio
core-dominated quasars with extremely broad H-beta emission lines that we
hypothesise may represent recent black hole mergers.
