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Upper Limits on the Presence of Central Massive Black Holes in Two Ultra-compact Dwarf Galaxies in Centaurus A
The Astrophysical Journal (2018)
  • Karina T. Voggel, University of Utah
  • Anil C. Seth, University of Utah
  • Nadine Neumayer, Max Planck Institute for Astronomy
  • Steffen Mieske, European Southern Observatory
  • Igor Chilingarian, Smithsonian Astrophysical Observatory
  • Christopher P. Ahn, University of Utah
  • Holger Baumgardt, University of Queensland
  • Michael Hilker, European Southern Observatory
  • Dieu D. Nguyen, University of Utah
  • Aaron J. Romanowsky, San Jose State University
  • Jonelle L. Walsh, Texas A & M University - College Station
  • Mark den Brok, ETH Zurich
  • Jay Strader, Michigan State University
The recent discovery of massive black holes (BHs) in the centers of high-mass ultra-compact dwarf galaxies (UCDs) suggests that at least some are the stripped nuclear star clusters of dwarf galaxies. We present the first study that investigates whether such massive BHs, and therefore stripped nuclei, also exist in low-mass (M < 107 M ) UCDs. We constrain the BH masses of two UCDs located in Centaurus A (UCD 320 and UCD 330) using Jeans modeling of the resolved stellar kinematics from adaptive optics data obtained with the SINFONI integral field spectrograph at the Very Large Telescope (VLT/SINFONI). No massive BHs are found in either UCD. We find a 3σ upper limit on the central BH mass in UCD 330 of M  < 1.0 × 105 M , which corresponds to 1.7% of the total mass. This excludes a high-mass fraction BH and would only allow low-mass BHs similar to those claimed to be detected in Local Group globular clusters. For UCD 320, poorer data quality results in a less constraining 3σ upper limit of M  < 1 × 106 M , which is equal to 37.7% of the total mass. The dynamical mass-to-light ratios of UCD 320 and UCD 330 are not inflated compared to predictions from stellar population models. The non-detection of BHs in these low-mass UCDs is consistent with the idea that elevated dynamical mass-to-light ratios do indicate the presence of a substantial BH. Although no massive BHs are detected, these systems could still be stripped nuclei. The strong rotation (v/σ of 0.3–0.4) in both UCDs and the two-component light profile in UCD 330 support the idea that these UCDs may be stripped nuclei of low-mass galaxies whose BH occupation fraction is not yet known.
  • galaxies: dwarf,
  • galaxies: kinematics and dynamics,
  • galaxies: nuclei,
  • galaxies: star clusters: general
Publication Date
April 27, 2018
Publisher Statement
This article was originally published in The Astrophysical Journal, volume 858, issue 1. © 2018. The American Astronomical Society. All rights reserved.

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Citation Information
Karina T. Voggel, Anil C. Seth, Nadine Neumayer, Steffen Mieske, et al.. "Upper Limits on the Presence of Central Massive Black Holes in Two Ultra-compact Dwarf Galaxies in Centaurus A" The Astrophysical Journal Vol. 858 Iss. 1 (2018) ISSN: 0004-637X
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