Dwarf Seyfert 1 Nuclei and the Low-mass End of the Mbh −σ Relation

To examine the relationship between black hole mass and host galaxy velocity dispersion for low black hole masses, we have measured the velocity dispersions of 15 Seyfert 1 galaxies from the catalog of Greene & Ho (2004). These Seyferts were selected from the Sloan Digital Sky Survey to have estimated black hole masses below 106 M⊙. The data are consistent with a straightforward downward extrapolation of the local MBH − σ relation, indicating that this correlation extends over a range of more than four orders of magnitude in black hole mass. The rms scatter of the sample about the extrapolated MBH −σ relation is 0.57 dex, consistent with the expected scatter of single-epoch mass estimates for Seyfert 1 galaxies. Subject headings: galaxies: active — galaxies: kinematics and dynamics — galaxies: nuclei — galaxies: Seyfert