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We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations of CO(2â€"1) emission from the circumnuclear disks in two early-type galaxies, NGC 1380 and NGC 6861. The disk in each galaxy is highly inclined (i ∼ 75°), and the projected velocities of the molecular gas near the galaxy centers are ∼300 km sâˆ'1 in NGC 1380 and ∼500 km sâˆ'1 in NGC 6861. We fit thin disk dynamical models to the ALMA data cubes to constrain the masses of the central black holes (BHs). We created host galaxy models using Hubble Space Telescope images for the extended stellar mass distributions and incorporated a range of plausible central dust extinction values. For NGC 1380, our best-fit model yields M BH = 1.47 Ă— 108 M ⊙ with a ∼40% uncertainty. For NGC 6861, the lack of dynamical tracers within the BH’s sphere of influence due to a central hole in the gas distribution precludes a precise measurement of M BH. However, our model fits require a value for M BH in the range of (1â€"3) Ă— 109 M ⊙ in NGC 6861 to reproduce the observations. The BH masses are generally consistent with predictions from local BHâ€"host galaxy scaling relations. Systematic uncertainties associated with dust extinction of the host galaxy light and choice of host galaxy mass model dominate the error budget of both measurements. Despite these limitations, the measurements demonstrate ALMA’s ability to provide constraints on BH masses in cases where the BH’s projected radius of influence is marginally resolved or the gas distribution has a central hole. [ABSTRACT FROM AUTHOR]

We present 0.″14 resolution Atacama Large Millimeter/submillimeter Array (ALMA) CO(2âˆ'1) observations of the circumnuclear gas disk in UGC 2698, a local compact galaxy. The disk exhibits regular rotation with projected velocities rising to 450 km sâˆ'1 near the galaxy center. We fit gas-dynamical models to the ALMA data cube, assuming the CO emission originates from a dynamically cold, thin disk, and measured the mass of the supermassive black hole (BH) in UGC 2698 to be M BH = (2.46 ± 0.07 [1 σ statistical] âˆ' 0.78 + 0.70 [systematic]) Ă— 109 M ⊙. UGC 2698 is part of a sample of nearby early-type galaxies that are plausible z ∼ 2 red nugget relics. Previous stellar-dynamical modeling for three galaxies in the sample found BH masses consistent with the BH massâˆ'stellar velocity dispersion (M BH âˆ' σ ⋆) relation but over-massive relative to the BH massâˆ'bulge luminosity (M BH âˆ' L bul) correlation, suggesting that BHs may gain the majority of their mass before their host galaxies. However, UGC 2698 is consistent with both M BH âˆ' σ ⋆ and M BH âˆ' L bul. As UGC 2698 has the largest stellar mass and effective radius in the local compact galaxy sample, it may have undergone more recent mergers that brought it in line with the BH scaling relations. Alternatively, given that the three previously measured compact galaxies are outliers from M BH âˆ' L bul, while UGC 2698 is not, there may be significant scatter at the poorly sampled high-mass end of the relation. Additional gas-dynamical M BH measurements for the compact galaxy sample will improve our understanding of BHâˆ'galaxy co-evolution. [ABSTRACT FROM AUTHOR]

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 5 and Cycle 6 observations of CO (2−1) and CO (3−2) emission at 0.″2−0.″3 resolution in two radio-bright, brightest group/cluster early-type galaxies, NGC 315 and NGC 4261. The data resolve CO emission that extends within their black hole (BH) spheres of influence (rg), tracing regular Keplerian rotation down to just tens of parsecs from the BHs. The projected molecular gas speeds in the highly inclined (i ≳ 60°) disks rise at least to 500 km s−1 near their galaxy centers. We fit dynamical models of thin-disk rotation directly to the ALMA data cubes and account for the extended stellar mass distributions by constructing galaxy surface brightness profiles corrected for a range of plausible dust extinction values. The best-fit models yield for NGC 315 and for NGC 4261, the latter of which is larger than previous estimates by a factor of ∼3. The BH masses are broadly consistent with the relations between BH masses and host galaxy properties. These are among the first ALMA observations to map dynamically cold gas kinematics well within the BH-dominated regions of radio galaxies, resolving the respective rg by factors of ∼5−10. The observations demonstrate ALMA's ability to precisely measure BH masses in active galaxies, which will enable more confident probes of accretion physics for the most massive galaxies. [ABSTRACT FROM AUTHOR]