Circumnuclear Gas in Seyfert 1 Galaxies: Morphology, Kinematics, and Direct Measurement of Black Hole Masses

The two-dimensional (2D) distribution and kinematics of the molecular, ionized, and highly ionized gas in the nuclear regions of Seyfert 1 galaxies have been measured using high spatial resolution (~0.09'') near-infrared spectroscopy from NIRSPEC with adaptive optics on the Keck telescope. Molecular hydrogen, H₂, is detected in all nine Seyfert 1 galaxies and, in the majority of galaxies, has a spatially resolved flux distribution. In contrast, the narrow component of the Brγ emission has a distribution consistent with that of the K-band continuum. In general, the kinematics of the molecular hydrogen is consistent with thin disk rotation, with a velocity gradient of over 100 km s⁻¹ measured across the central 0.5'' in three galaxies, and a similar gradient across the central 1.5'' in an additional two galaxies. The kinematics of Brγ is in agreement with the H₂ rotation, except that in all four cases the central 0.5'' is either blue- or redshifted by more than 75 km s⁻¹. The highly ionized gas, measured with the [Ca VIII] and [Si VII] coronal lines, is spatially and kinematically consistent with Brγ in the central 0.5''. In addition, the velocity dispersion of both the coronal and Brγ emission is greater than that of H₂ (by 1.3-2.0 times), suggesting that both originate from gas that is located closer to the nucleus than the H₂ line emitting gas. Dynamical models have been fitted to the 2D H₂ kinematics, taking into account the stellar mass distribution, the emission line flux distribution, and the point spread function. For NGC 3227 the modeling indicates a black hole mass of M_BH = 2.0^{+ 1.0}_−0.4 × 10⁷ M_☉, and for NGC 4151 M_BH = 3.0^{+ 0.75}_−2.2 × 10⁷ M_☉. In NGC 7469 the best-fit model gives M_BH < 5.0 × 10⁷ M_☉. In all three galaxies, modeling suggests a near face-on disk inclination angle, which is consistent with the unification theory of active galaxies. The direct black hole mass estimates verify that masses determined from technique of reverberation mapping are accurate to within a factor of 3 with no additional systematic errors.