Exploring the Low-Mass End of The M-Sigma Relation with Active Galaxies
  We present new measurements of stellar velocity dispersions, using spectra
obtained with the Keck Echellette Spectrograph and Imager (ESI) and the
Magellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalogue
of Greene & Ho. These objects were selected from the Sloan Digital Sky Survey
(SDSS) to have estimated black hole (BH) masses below 2\times10^6 M\odot.
Combining our results with previous ESI observations of similar objects, we
obtain an expanded sample of 93 galaxies and examine the relation between BH
mass and velocity dispersion (the M-Sigma relation) for active galaxies with
low BH masses. The low-mass active galaxies tend to follow the extrapolation of
the M-Sigma relation of inactive galaxies. Including results for active
galaxies of higher BH mass from the literature, we find a zero point{\alpha}=
7.68\pm0.08 and slope of {\beta}= 3.32\pm0.22 for the M-Sigma relation [in the
form log Mbh={\alpha}+{\beta}log({\sigma}*/200 km s-1)], with intrinsic scatter
of 0.46\pm0.03 dex. This result is consistent, within the uncertainties, with
the slope of the M-Sigma relation for reverberation-mapped active galaxies with
BH masses from 10^6 to 10^9 M\odot. For the subset of our sample having
morphological information from Hubble Space Telescope images, we examine the
slope of the M-Sigma relation separately for subsamples of barred and unbarred
host galaxies, and find no significant evidence for a difference in slope. We
do find a mild offset between low-inclination and high-inclination disk
galaxies, such that more highly inclined galaxies tend to have larger {\sigma}*
at a given value of BH mass, presumably due to the contribution of disk
rotation within the spectroscopic aperture. We also find that the velocity
dispersion of the ionized gas trace the stellar velocity dispersion well for
this large sample of low-mass Seyfert 1 galaxies.
