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We present 0$.\!\!^{\prime\prime}{22}$-resolution CO(2$-$1) observations of the circumnuclear gas disk in the local compact galaxy NGC 384 with the Atacama Large Millimeter/submillimeter Array (ALMA). While the majority of the disk displays regular rotation with projected velocities rising to $370$ km s$^{-1}$, the inner $\sim$0\farcs{5} exhibits a kinematic twist. We develop warped disk gas-dynamical models to account for this twist, fit those models to the ALMA data cube, and find a stellar mass-to-light ratio in the $H$-band of \mlabstract\ and a supermassive black hole (BH) mass ($M_{\mathrm{BH}}$) of $M_{\mathrm{BH}}$ $= (7.26^{+0.43}_{-0.48}$ [$1\sigma$ statistical] $^{+0.55}_{-1.00}$ [systematic])$\times 10^8$ $M_\odot$. In contrast to most previous dynamical $M_{\mathrm{BH}}$ measurements in local compact galaxies, which typically found over-massive BHs compared to the local BH mass$-$bulge luminosity and BH mass$-$bulge mass relations, NGC 384 lies within the scatter of those scaling relations. NGC 384 and other local compact galaxies are likely relics of $z\sim2$ red nuggets, and over-massive BHs in these relics indicate BH growth may conclude before the host galaxy stars have finished assembly. Our NGC 384 results may challenge this evolutionary picture, suggesting there may be increased scatter in the scaling relations than previously thought. However, this scatter could be inflated by systematic differences between stellar- and gas-dynamical measurement methods, motivating direct comparisons between the methods for NGC 384 and the other compact galaxies in the sample., Comment: 19 pages, 8 figures, accepted for publication in ApJ

Dusty circumnuclear disks (CNDs) in luminous early-type galaxies (ETGs) show regular, dynamically cold molecular gas kinematics. For a growing number of ETGs, Atacama Large Millimeter/sub-millimeter Array (ALMA) CO imaging and detailed gas-dynamical modeling facilitate moderate-to-high precision black hole (BH) mass ($M_{BH}$) determinations. From the ALMA archive, we identified a subset of 26 ETGs with estimated $M_{BH}/M_{\odot} \gtrsim 10^8$ to a few $\times$10$^9$ and clean CO kinematics but that previously did not have sufficiently high angular resolution near-IR observations to mitigate dust obscuration when constructing stellar luminosity models. We present new optical and near-IR Hubble Space Telescope (HST) images of this sample to supplement the archival HST data, detailing the sample properties and data analysis techniques. After masking the most apparent dust features, we measure stellar surface brightness profiles and model the luminosities using the multi-Gaussian expansion (MGE) formalism. Some of these MGEs have already been used in CO dynamical modeling efforts to secure quality \mbh\ determinations, and the remaining ETG targets here are expected to significantly improve the high-mass end of the current BH census, facilitating new scrutiny of local BH mass-host galaxy scaling relationships. We also explore stellar isophotal behavior and general dust properties, finding these CNDs generally become optically thick in the near-IR ($A_H \gtrsim 1$ mag). These CNDs are typically well-aligned with the larger-scale stellar photometric axes with a few notable exceptions. Uncertain dust impact on the MGE often dominates the BH mass error budget, so extensions of this work will focus on constraining CND dust attenuation., Comment: 47 pages, 37 Figures, Accepted for publication in ApJ

We present molecular gas-dynamical mass measurements of the central black holes in the giant elliptical galaxies NGC 4786 and NGC 5193, based on CO(2$-$1) observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope near-infrared imaging. The central region in each galaxy contains a circumnuclear disk that exhibits orderly rotation with projected line-of-sight velocities of ${\sim} 270\, \mathrm{km}\,\mathrm{s^{-1}}$. We build gas-dynamical models for the rotating disk in each galaxy and fit them directly to the ALMA data cubes. At $0.31^{\prime \prime}$resolution, the ALMA observations do not fully resolve the black hole sphere of influence (SOI), and neither galaxy exhibits a central rise in rotation speed, indicating that emission from deep within the SOI is not detected. As a result, our models do not tightly constrain the central black hole mass in either galaxy, but they prefer the presence of a central massive object in both galaxies. We measure the black hole mass to be $(M_{\mathrm{BH}}/10^8\, M_{\odot}) = 5.0 \pm 0.2 \,[\mathrm{1\sigma \,statistical}] \,^{+1.4}_{-1.3} \,[\mathrm{systematic}]$ in NGC 4786 and $(M_{\mathrm{BH}}/10^8\, M_{\odot}) = 1.4 \pm 0.03 \, [\mathrm{1\sigma\,statistical}] ^{+1.5}_{-0.1} \,[\mathrm{systematic}]$ in NGC 5193. The largest component of each measurement's error budget is from the systematic uncertainty associated with the extinction correction in the host galaxy models. This underscores the importance of assessing the impact of dust attenuation on the inferred $M_{\mathrm{BH}}$., Comment: 24 pages, 8 figures. Accepted for publication in ApJ