Stellar velocity dispersion in NLS1 galaxies

Abstract

Several authors recently explored the Black-Hole mass (M_BH) vs. stellar velocity dispersion (sigma_*) relationship for Narrow Line Seyfert 1 galaxies (NLS1s). Their results are more or less in agreement and seem to indicate that NLS1s fill the region below the fit obtained by Tremaine et al. (2002), showing a range of sigma_* similar to that of Seyfert 1 galaxies, and a lower M_BH. Until now the [O III] width has been used in place of the stellar velocity dispersion, but some indications begin to arise against the effectiveness of the gaseous kinematics in representing the bulge potential at least in NLS1s. Bian & Zhao (2004) stressed the urgency to produce true sigma_* measurements. Here we present new stellar velocity dispersions obtained through direct measurements of the Ca II absorption triplet (~ 8550 A) in the nuclei of 8 NLS1 galaxies. The resulting sigma_* values and a comparison with sigma_[O III] confirm our suspects (see Botte et al. 2004) that [O III] typically overestimates the stellar velocity dispersion and demonstrate that NLS1s follow the M_BH-sigma_* relation as Seyfert 1, quasars and non-active galaxies.