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

Christopher P. Ahn, Anil C. Seth, Michele Cappellari, Davor Krajnović, Jay Strader, Karina T. Voggel, Jonelle L. Walsh, Arash Bahramian, Holger Baumgardt, Jean Brodie, Igor Chilingarian, Laura Chomiuk, Mark Den Brok, Matthias Frank, Michael Hilker, Richard M. McDermid, Steffen Mieske, Nadine Neumayer, Dieu D. Nguyen, Renuka Pechetti & 2 others Aaron J. Romanowsky, Lee Spitler

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Abstract

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+2.1-1.7 × 10M⊙ (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.

Original languageEnglish
Article number102
Pages (from-to)1-16
Number of pages16
JournalAstrophysical Journal
Volume858
Issue number2
DOIs
Publication statusPublished - 10 May 2018

Bibliographical note

Copyright 2018 The American Astronomical Society. First published in the Astrophysical journal, 858(2), 102, 2018, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/aabc57. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • galaxies: clusters: general
  • galaxies: dwarf
  • galaxies: evolution
  • galaxies: formation
  • galaxies: kinematics and dynamics

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