The Sloan Digital Sky Survey Reverberation Mapping Project: The
  M_BH-Host Relations at 0.2<z<0.6 from Reverberation Mapping and Hubble Space
  Telescope Imaging
  We present the results of a pilot Hubble Space Telescope (HST) imaging study
of the host galaxies of ten quasars from the Sloan Digital Sky Survey
Reverberation Mapping (SDSS-RM) project. Probing more than an order of
magnitude in BH and stellar masses, our sample is the first statistical sample
to study the BH-host correlations beyond z>0.3 with reliable BH masses from
reverberation mapping rather than from single-epoch spectroscopy. We perform
image decomposition in two HST bands (UVIS-F606W and IR-F110W) to measure host
colors and estimate stellar masses using empirical relations between broad-band
colors and the mass-to-light ratio. The stellar masses of our targets are
mostly dominated by a bulge component. The BH masses and stellar masses of our
sample broadly follow the same correlations found for local RM AGN and
quiescent bulge-dominant galaxies, with no strong evidence of evolution in the
M_BH-M_*,bulge relation to z~0.6. We further compare the host light fraction
from HST imaging decomposition to that estimated from spectral decomposition.
We found a good correlation between the host fractions derived with both
methods. However, the host fraction derived from spectral decomposition is
systematically smaller than that from imaging decomposition by ~30%, indicating
different systematics in both approaches. This study paves the way for upcoming
more ambitious host galaxy studies of quasars with direct RM-based BH masses at
high redshift.
