2019ApJ...880...68R

We present H I 21 cm spectroscopy from the Robert C. Byrd Green Bank Telescope for the host galaxies of 31 nearby active galactic nuclei with direct M_BH measurements from reverberation mapping. These are the first published H I detections for 12 galaxies, and the spectral quality is generally an improvement over archival data for the remainder of the sample. We present measurements of emission-line fluxes, velocity widths, and recessional velocities from which we derive H I mass, total gas mass, and redshifts. Combining M_GAS with constraints on M_STARS allows exploration of the baryonic content of these galaxies. We find a typical M_GAS/M_STARS fraction of 10%, with a few reaching ∼30%-50%. We also examine several relationships between M_STARS, M_GAS, M_BH, baryonic mass, and morphological type. We find a weak preference for galaxies with larger M_GAS to host more massive black holes. We also find gas-to-stellar fractions to weakly correlate with later types in unbarred spirals, with an approximately constant fraction for barred spirals. Consistent with previous studies, we find declining M_GAS/M_STARS with increasing M_STARS, with a slope suggesting the gas reservoirs have been replenished. Finally, we find a clear relationship for M_BH-M_BARY with a similar slope as M_BH-M_STARS reported by Bentz & Manne-Nicholas. The dwarf Seyfert NGC 4395 appears to follow this relationship as well, even though it has a significantly higher gas fraction and smaller M_BH than the remainder of our sample.