The Diverse Morphology, Stellar Population, and Black Hole Scaling
  Relations of the Host Galaxies of Nearby Quasars
  We present rest-frame $B$ and $I$ imaging of 35 low-redshift ($z < 0.5$)
Palomar-Green quasars using the Hubble Space Telescope Wide Field Camera 3. We
perform multi-component two-dimensional image decomposition to separate the
host galaxy from its bright active nucleus, characterize its morphology, and
measure its photometric properties. Special care is devoted to quantifying the
structural parameters of the galaxy bulge, determine its $B-I$ color, and
estimate its stellar mass. Roughly half of the sample, comprising the less
luminous ($L_{5100} \lesssim 10^{45}\,\mathrm{erg\,s^{-1}}$) but most high
Eddington ratio quasars, reside in disk galaxies that are often barred and
possess pseudo bulges. The large stellar masses, large effective radii, and
faint surface brightnesses suggest that the host galaxies of the most luminous
quasars are mostly ellipticals. Major mergers constitute only a minority
($\lesssim 20\%$) of our sample. Our quasar sample roughly obeys the scaling
relations between black hole mass and host galaxy (bulge, core, total) stellar
mass. Hosts with black holes more massive than $\sim 10^8\,M_\odot$ behave
similarly to classical bulges and early-type galaxies, while those with less
massive black holes, particular the narrow-line Seyfert 1s, are consistent with
pseudo bulges in late-type galaxies. The host galaxy bulges, irrespective of
whether they are classical or pseudo, follow the relatively tight inverse
relation between effective radius and mean effective surface brightness of
inactive classical bulges and ellipticals. We argue that pseudo bulges
experience recent or ongoing nuclear star formation.
