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Title: A globular cluster toward M87 with a radial velocity < – 1000 km s{sup –1}: the first hypervelocity cluster

We report the discovery of an object near M87 in the Virgo Cluster with an extraordinary blueshift of –1025 km s{sup –1}, offset from the systemic velocity by >2300 km s{sup –1}. Evaluation of photometric and spectroscopic data provides strong evidence that this object is a distant massive globular cluster, which we call HVGC-1 in analogy to Galactic hypervelocity stars. We consider but disfavor more exotic interpretations, such as a system of stars bound to a recoiling black hole. The odds of observing an outlier as extreme as HVGC-1 in a virialized distribution of intracluster objects are small; it appears more likely that the cluster was (or is being) ejected from Virgo following a three-body interaction. The nature of the interaction is unclear, and could involve either a subhalo or a binary supermassive black hole at the center of M87.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [6]
  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
  2. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
  3. Department of Physics and Astronomy, San José State University, San Jose, CA 95192 (United States)
  4. University of California Observatories, Santa Cruz, CA 95064 (United States)
  5. Institute for Theoretical Physics, University of Zurich, CH-8057 Zurich (Switzerland)
  6. Department of Astronomy, University of California, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22365837
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; BLACK HOLES; EVALUATION; GALAXY CLUSTERS; MILKY WAY; RADIAL VELOCITY; RECOILS; STAR CLUSTERS; THREE-BODY PROBLEM