A Local Baseline of the Black Hole Mass Scaling Relations for Active Galaxies. III. The BH mass – $σ$ relation [GA]


We create a baseline of the black hole (BH) mass ($M_{\rm BH}$) – stellar-velocity dispersion ($\sigma$) relation for active galaxies, using a homogeneous sample of 66 Seyfert-1 galaxies in the local Universe (0.02 $< z <$ 0.09) selected from the Sloan Digital Sky Survey (SDSS). A multi-filter analysis of SDSS images yields AGN luminosities free of host-galaxy contamination. High signal-to-noise ratio Keck spectra provide the width of the broad H$\beta$ emission line free of FeII emission and stellar absorption. $M_{\rm BH}$ is estimated following the virial method. The Keck long-slit spectra provide spatially-resolved kinematics that is used to determine the rotation-free stellar-velocity dispersion within the spheroid effective radius ($\sigma_{\rm reff}$). To probe the effect of the kinematically-cold but rotationally-supported disk component, present in the majority of host galaxies, on aperture sigma measurements, we determine the stellar-velocity dispersion within an aperture of the size of the SDSS fiber ($\sigma_{\rm ap}$). While for face-on objects, the effect is negligible, for edge-on galaxies, rotational broadening causes $\sigma_{\rm ap}$ to be overestimated by on average 16$\pm$3%, showing the importance of spatially-resolved kinematics for a sample of late-type galaxies. Overall, our Seyfert-1 galaxy sample follows the same $M_{\rm BH}$-$\sigma$ relation as that of reverberation-mapped active galaxies as well as quiescent galaxies, with a comparable scatter when considering $\sigma_{\rm reff}$. We find evidence for host galaxies with a spheroidal component classified as pseudo bulge to scatter less than their classical counterparts, suggestive of secular evolution providing an efficient and synchronized way in growing both BHs and spheroids for spiral galaxies.

Read this paper on arXiv…

V. Bennert, T. Treu, M. Auger, et. al.
Wed, 17 Sep 14

Comments: 14 pages, 6 figures, 4 tables, submitted to ApJ