A Population of Luminous Globular Clusters and Stripped Nuclei with Elevated Mass to Light Ratios around NGC 5128 - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical Journal Year : 2022

A Population of Luminous Globular Clusters and Stripped Nuclei with Elevated Mass to Light Ratios around NGC 5128

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1
Antoine Dumont
  • Function : Author
Anil C. Seth
  • Function : Author
Jay Strader
Karina Voggel
David J. Sand
  • Function : Author
Allison K. Hughes
  • Function : Author
Nelson Caldwell
Denija Crnojević
  • Function : Author
Mario Mateo
  • Function : Author
John I. Bailey
  • Function : Author
Duncan A. Forbes
  • Function : Author

Abstract

The dense central regions of tidally disrupted galaxies can survive as ultracompact dwarfs (UCDs) that hide among the luminous globular clusters (GCs) in the halo of massive galaxies. An exciting confirmation of this model is the detection of overmassive black holes in the centers of some UCDs, which also lead to elevated dynamical mass-to-light ratios (M/L dyn). Here we present new high-resolution spectroscopic observations of 321 luminous GC candidates in the massive galaxy NGC 5128/Centaurus A. Using these data we confirm 27 new luminous GCs, and measure velocity dispersions for 57 luminous GCs (with g-band luminosities between 2.5 × 105 and 2.5 × 107 L ), of which 48 are new measurements. Combining these data with size measurements from Gaia, we determine the M/L dyn for all 57 luminous GCs. We see a clear bimodality in the M/L dyn distribution, with a population of normal GCs with mean M/L dyn = 1.51 ± 0.31, and a second population of ~20 GCs with elevated mean M/L dyn = 2.68 ± 0.22. We show that black holes with masses ~4%-18% of the luminous GCs can explain the elevated mass-to-light ratios. Hence, it is plausible that the NGC 5128 sources with elevated M/L dyn are mostly stripped galaxy nuclei that contain massive central black holes, though future high spatial resolution observations are necessary to confirm this hypothesis for individual sources. We also present a detailed discussion of an extreme outlier, VHH81-01, one of the largest and most massive GC in NGC 5128, making it an exceptionally strong candidate to be a tidally stripped nucleus. * This paper includes data gathered with the 6.5 m Magellan Telescope at Las Campanas Observatory, Chile.
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Dates and versions

insu-03668896 , version 1 (16-05-2022)

Licence

Attribution - CC BY 4.0

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Antoine Dumont, Anil C. Seth, Jay Strader, Karina Voggel, David J. Sand, et al.. A Population of Luminous Globular Clusters and Stripped Nuclei with Elevated Mass to Light Ratios around NGC 5128. The Astrophysical Journal, 2022, 929, ⟨10.3847/1538-4357/ac551c⟩. ⟨insu-03668896⟩
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