Correlations of Quasar Optical Spectra with Radio Morphology
  (Abridged) With the largest homogeneous quasar sample with optical spectra
and robust radio morphology classifications assembled to date, we investigate
quasar radio and optical properties with unprecedented statistical power. The
data consist of 4714 radio quasars from FIRST with S_{20}>2mJy and SDSS
spectra. Radio morphology classes include core-only (core), core-lobe (lobe),
core-jet (jet), lobe-core-lobe (triple), and double-lobe. We examine the
optical colors of radio-morphology subsamples and find that radio quasars with
core emission unresolved by FIRST (on 5" scale) have a redder color
distribution than radio-quiet quasars (S_{20}<1mJy); other classes of radio
quasars have optical color distributions similar to the radio-quiet quasars.
This analysis also suggests that optical colors of z<2.7 SDSS quasars are not
strongly (<0.1mag) biased blue. We show that the radio core-to-lobe flux
density ratio (R) and the radio-to-optical (i-band) ratio of the quasar core
(RI) are correlated, suggesting that both parameters are indicative of
line-of-sight orientation. We investigate spectral line equivalent widths as a
function of R and RI, including the [OIII] narrow line doublet and the CIV
{\lambda}1549 and MgII {\lambda}2799 broad lines. We find that the rest
equivalent widths (EWs) of the broad lines correlate positively with RI at the
4-8{\sigma} level. But we find no strong dependence of EW on R, in contrast to
previous results. One interpretation is that EWs increase as the line-of-sight
angle to the radio-jet axis decreases. These results are in stark contrast to
commonly accepted orientation-based theories, which suggest that continuum
emission should increase as the angle to the radio-jet axis decreases,
resulting in smaller EW of emission lines (assumed isotropic). Finally, we find
that the Baldwin effect in our sample does not depend on quasar radio
morphology.
