The black hole in the most massive ultracompact dwarf galaxy M59-UCD3

Journal article

We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive-optics-assisted near-IR integral field spectroscopy from Gemini/NIFS and Hubble Space Telescope (HST) imaging. We use the multiband HST imaging to create a mass model that suggests and accounts for the presence of multiple stellar populations and structural components. We combine these mass models with kinematics measurements from Gemini/NIFS to find a best-fit stellar mass-to-light ratio (M/L) and black hole (BH) mass using Jeans anisotropic models (JAMs), axisymmetric Schwarzschild models, and triaxial Schwarzschild models. The best-fit parameters in the JAM and axisymmetric Schwarzschild models have BHs between 2.5 and 5.9 million solar masses. The triaxial Schwarzschild models point toward a similar BH mass but show a minimum χ 2 at a BH mass of ~0. Models with a BH in all three techniques provide better fits to the central V rms profiles, and thus we estimate the BH mass to be ${4.2}_{-1.7}^{+2.1}\times {10}^{6}$ M ⊙ (estimated 1σ uncertainties). We also present deep radio imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass measurements, and we compare these to X-ray measurements to check for consistency with the fundamental plane of BH accretion. We detect faint radio emission in M59cO but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray detections in both these sources. The BH mass and nuclear light profile of M59-UCD3 suggest that it is the tidally stripped remnant of a ~109–1010 M ⊙ galaxy.

Authors: Ahn, C; Seth, A; Cappellari, M; al., E

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: Astrophysical Journal
• Volume: 858
• Issue: 2
• Article number: 102
• Publication date: 2018-05-11
• Acceptance date: 2018-04-06
• DOI: 10.3847/1538-4357/aabc57
• EISSN: 1538-4357
• ISSN: 0004-637X
• Keywords: galaxies: dwarf; galaxies:formation; galaxies:clusters; galaxies:black holes; galaxies: kinematics and dynamics