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An Enigmatic Population of Luminous Globular Clusters in a Galaxy Lacking Dark Matter
The Astrophysical Journal Letters (2018)
  • Pieter G. van Dokkum, Yale University
  • Yotam Cohen, Yale University
  • Shany Danieli, Yale University
  • J. M. Diederik Kruijssen, Zentrum für Astronomie der Universität Heidelberg
  • Aaron J. Romanowsky, San Jose State University
  • Allison Merritt, Max-Planck-Institut für Astronomie
  • Roberto Abraham, University of Toronto
  • Jean P. Brodie, University of California Observatories
  • Charlie Conroy, Harvard-Smithsonian Center for Astrophysics
  • Deborah Lokhorst, University of Toronto
  • Lamiya Mowla, Yale University
  • Ewan O'Sullivan, Harvard-Smithsonian Center for Astrophysics
  • Jielai Zhang, University of Toronto
We recently found an ultra diffuse galaxy (UDG) with a half-light radius of R e  = 2.2 kpc and little or no dark matter. The total mass of NGC1052–DF2 was measured from the radial velocities of bright compact objects that are associated with the galaxy. Here, we analyze these objects using a combination of Hubble Space Telescope (HST) imaging and Keck spectroscopy. Their average size is  pc and their average ellipticity is . From a stacked Keck spectrum we derive an age of 9 Gyr and a metallicity of [Fe/H] = −1.35 ± 0.12. Their properties are similar to ωCentauri, the brightest and largest globular cluster in the Milky Way, and our results demonstrate that the luminosity function of metal-poor globular clusters is not universal. The fraction of the total stellar mass that is in the globular cluster system is similar to that in other UDGs, and consistent with "failed galaxy" scenarios, where star formation terminated shortly after the clusters were formed. However, the galaxy is a factor of ~1000 removed from the relation between globular cluster mass and total galaxy mass that has been found for other galaxies, including other UDGs. We infer that a dark matter halo is not a prerequisite for the formation of metal-poor globular cluster-like objects in high-redshift galaxies.
Publication Date
April, 2018
Publisher Statement
This article was originally published in The Astrophysical Journal Letters, volume 856, issue 2. © 2018. The American Astronomical Society. All rights reserved.

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Citation Information
Pieter G. van Dokkum, Yotam Cohen, Shany Danieli, J. M. Diederik Kruijssen, et al.. "An Enigmatic Population of Luminous Globular Clusters in a Galaxy Lacking Dark Matter" The Astrophysical Journal Letters Vol. 856 Iss. 2 (2018) ISSN: 2041-8205
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