2009ApJ...699..638H

We combine ionized gas ([N II] λ6583) and stellar central velocity dispersions for a sample of 345 galaxies, with and without active galactic nuclei (AGNs), to study the dynamical state of the nuclear gas and its physical origin. The gas dispersions strongly correlate with the stellar dispersions over the velocity range of σ ~ 30-350 km/s, such that σ_ g_/σ*_~ 0.6-1.4, with an average value of 0.80. These results are independent of Hubble type (for galaxies from E to Sbc), the presence or absence of a bar, or local galaxy environment. For galaxies of type Sc and later and that have σ_*≲ 40 km/s, the gas seems to have a minimum threshold of σ_g~ 30 km/s, such that σ_ g_/σ*_ always exceeds 1. Within the sample of AGNs, σ_g/σ_* increases with nuclear luminosity or Eddington ratio, a possible manifestation of AGN feedback associated with accretion disk winds or outflows. This extra source of nongravitational line broadening should be removed when trying to use σ_g to estimate σ_*. We show that the mass budget of the narrow-line region (NLR) can be accounted for by mass loss from evolved stars. The kinematics of the gas, dominated by random motions, largely reflect the velocity field of the hot gas in the bulge. Lastly, we offer a simple explanation for the correlation between line width and line luminosity observed in the NLR of AGNs.