Dwarf seyfert 1 nuclei and the low-mass end of the M_BH-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 recent catalog of Greene & Ho. These Seyfert galaxies were selected from the Sloan Digital Sky Survey to have estimated black hole masses below 10 ⁶ M_⊙. The data are consistent with a straightforward downward extrapolation of the local M_BH-σ relation, indicating that this correlation extends over a range of more than 4 orders of magnitude in black hole mass. The rms scatter of the sample about the extrapolated M_BH-σ relation is 0.57 dex, consistent with the expected scatter of single-epoch mass estimates for Seyfert 1 galaxies.