EXPLORING THE LOW-MASS END OF THE<i>M</i>_BH-σ_*RELATION WITH ACTIVE GALAXIES

Abstract

We present new measurements of stellar velocity dispersions, using spectra\nobtained with the Keck Echellette Spectrograph and Imager (ESI) and the\nMagellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalogue\nof Greene &amp; Ho. These objects were selected from the Sloan Digital Sky Survey\n(SDSS) to have estimated black hole (BH) masses below 2\\times10^6 M\\odot.\nCombining our results with previous ESI observations of similar objects, we\nobtain an expanded sample of 93 galaxies and examine the relation between BH\nmass and velocity dispersion (the M-Sigma relation) for active galaxies with\nlow BH masses. The low-mass active galaxies tend to follow the extrapolation of\nthe M-Sigma relation of inactive galaxies. Including results for active\ngalaxies of higher BH mass from the literature, we find a zero point{\\alpha}=\n7.68\\pm0.08 and slope of {\\beta}= 3.32\\pm0.22 for the M-Sigma relation [in the\nform log Mbh={\\alpha}+{\\beta}log({\\sigma}*/200 km s-1)], with intrinsic scatter\nof 0.46\\pm0.03 dex. This result is consistent, within the uncertainties, with\nthe slope of the M-Sigma relation for reverberation-mapped active galaxies with\nBH masses from 10^6 to 10^9 M\\odot. For the subset of our sample having\nmorphological information from Hubble Space Telescope images, we examine the\nslope of the M-Sigma relation separately for subsamples of barred and unbarred\nhost galaxies, and find no significant evidence for a difference in slope. We\ndo find a mild offset between low-inclination and high-inclination disk\ngalaxies, such that more highly inclined galaxies tend to have larger {\\sigma}*\nat a given value of BH mass, presumably due to the contribution of disk\nrotation within the spectroscopic aperture. We also find that the velocity\ndispersion of the ionized gas trace the stellar velocity dispersion well for\nthis large sample of low-mass Seyfert 1 galaxies.\n