The MASSIVE survey – XIX. Molecular gas measurements of the supermassive black hole masses in the elliptical galaxies NGC 1684 and NGC 0997

Dominiak, Pandora, Bureau, Martin, Davis, Timothy A. ORCID: https://orcid.org/0000-0003-4932-9379, Ma, Chung-Pei, Greene, Jenny E. and Gu, Meng 2024. The MASSIVE survey – XIX. Molecular gas measurements of the supermassive black hole masses in the elliptical galaxies NGC 1684 and NGC 0997. Monthly Notices of the Royal Astronomical Society 529 (2) , pp. 1597-1616. 10.1093/mnras/stae314

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Abstract

Supermassive black hole (SMBH) masses can be measured by observing their dynamical effects on tracers, such as molecular gas. We present high angular resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 12CO(2-1) line emission of the early-type galaxies (ETGs) NGC 1684 and NGC 0997, obtained as part of the MASSIVE survey, a volume-limited integral-field spectroscopic study of the most massive local ETGs. NGC 1684 has a regularly-rotating central molecular gas disc, with a spatial extent of ≈6″ (≈1.8 kpc) in radius and a central hole slightly larger than the expected SMBH sphere of influence. We forward model the data cube in a Bayesian framework with the Kinematic Molecular Simulation (KinMS) code and infer a SMBH mass of M⊙ (3σ confidence interval) and a F110W-filter stellar mass-to-light ratio of (2.50 ± 0.05) M⊙/L⊙, F110W. NGC 0997 has a regularly-rotating central molecular gas disc, with a spatial extent of ≈5″ (≈2.2 kpc) in radius and a partially-filled central hole much larger than the expected SMBH sphere of influence, thus preventing a robust SMBH mass determination. With the same modelling method, we nevertheless constrain the SMBH mass to be in the range 4.0 × 107 to 1.8 × 109 M⊙ and the F160W-filter stellar mass-to-light ratio to be (1.52 ± 0.11) M⊙/L⊙, F160W. Both SMBH masses are consistent with the SMBH mass – stellar velocity dispersion (MBH – σe) relation, suggesting that the over-massive SMBHs present in other very massive ETGs are fairly uncommon.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	Oxford University Press
ISSN:	1365-2966
Date of First Compliant Deposit:	1 February 2024
Date of Acceptance:	29 January 2024
Last Modified:	17 Apr 2024 14:00
URI:	https://orca.cardiff.ac.uk/id/eprint/166034

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