Stellar velocity dispersion in narrow-line Seyfert 1 galaxies

Abstract

Several authors have recently explored, for narrow-line Seyfert 1 galaxies (NLS1s), the relationship between black hole mass (MBH) and stellar velocity dispersion (σ*). 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., showing a range of σ* similar to that of Seyfert 1 galaxies, and a lower MBH. Until now, the [Oiii] width has been used in place of the stellar velocity dispersion, but some indications have begun to arise against the effectiveness of the gaseous kinematics in representing the bulge potential, at least in NLS1s. Bian & Zhao have stressed the urgency of producing true σ* measurements. Here, we present new stellar velocity dispersions obtained through direct measurements of the Caii absorption triplet (∼8550 Å) in the nuclei of eight NLS1 galaxies. The resulting σ* values and a comparison with σ[OIII] confirm our suspicion that [Oiii] typically overestimates the stellar velocity dispersion. We demonstrate that NLS1s follow the MBH–σ* relation as Seyfert 1, quasars and non-active galaxies.