Precision Measurement of Black Hole Masses in Early-Type Galaxies from the ALMA Archive
Abstract
We have identified a sample of eighteen nearby early-type galaxies in the ALMA archive that are detected in CO at high S/N and show rotation-dominated kinematics. We anticipate that gas-dynamical modeling of their well-resolved molecular gas disks will result in black hole mass measurements with precisions of 20-30% or better, assuming the stellar luminosity profile can be accurately measured. Gas mass measurements and dust attenuation modeling suggest that the extinction may often exceed 1 mag in the H-band. Circumnuclear dust will significantly obscure the stellar light in even near-IR data and, in some cases, may lead to the dominant uncertainty in the black hole mass error budget. Our early-type galaxies have no prior wide-field HST IR observations, and we propose a single orbit of WFC3 data for each of these eighteen galaxies as a final step to obtaining robust black hole mass measurements. We will employ the IR channel for all targets and the UVIS channel for fourteen of them, which will supplement archival HST observations. Using HST imaging in filters from B to H bands, we will determine central extinction levels and produce corrected H-band stellar luminosity profiles that account for dust extinction uncertainties. This HST program will double the number of early-type galaxies with both clean ALMA CO disk rotation and high-quality HST IR imaging, and will significantly increase the number of luminous E/S0 galaxies for which we can confidently measure their black hole masses.
- Publication:
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HST Proposal
- Pub Date:
- June 2019
- Bibcode:
- 2019hst..prop15909B