The Relationship Between Black Hole Mass and Velocity Dispersion in Seyfert 1 Galaxies

Charles H. Nelson, Richard F. Green, Gary Bower, Karl Gebhardt, Donna Weistrop

Published 2004-07-18Version 1

Black hole masses in active galactic nuclei (AGN) are difficult to measure using conventional dynamical methods, but can be determined using the technique of reverberation mapping. However, it is important to verify that the results of these different methods are equivalent. This can be done indirectly, using scaling relations between the black hole and the host galaxy spheroid. For this purpose, we have obtained new measurements of the bulge stellar velocity dispersion, sigma, in Seyfert 1 galaxies. These are used in conjunction with the M_bh -- sigma relation to validate nuclear black hole masses, M_bh, in active galaxies determined through reverberation mapping. We find that Seyfert galaxies follow the same M_bh -- sigma relation as non-active galaxies, indicating that reverberation mapping measurements of M_bh are consistent with those obtained using other methods. We also reconsider the relationship between bulge absolute magnitude, M_bulge, and black hole mass. We find that Seyfert galaxies are offset from non-active galaxies, but that the deviation can be entirely understood as a difference in bulge luminosity, not black hole mass; Seyfert hosts are brighter than normal galaxies for a given value of their velocity dispersion, perhaps as a result of younger stellar populations.