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Title: A STACKED SEARCH FOR INTERMEDIATE-MASS BLACK HOLES IN 337 EXTRAGALACTIC STAR CLUSTERS

Forbes et al. recently used the Hubble Space Telescope to localize hundreds of candidate star clusters in NGC 1023, an early-type galaxy at a distance of 11.1 Mpc. Old stars dominate the light of 92% of the clusters and intermediate-age stars dominate the light of the remaining 8%. Theory predicts that clusters with such ages can host intermediate-mass black holes (IMBHs) with masses To investigate this prediction, we used 264 s of 5.5 GHz data from the Karl G. Jansky Very Large Array to search for the radiative signatures of IMBH accretion from 337 candidate clusters in an image spanning 492″ (26 kpc) with a resolution of 0.″40 (22 pc). None of the individual clusters are detected, nor are weighted-mean image stacks of the 311 old clusters, the 26 intermediate-age clusters, and the 20 clusters with stellar masses The clusters thus lack radio analogs of HLX-1, a strong IMBH candidate in a cluster in the early-type galaxy ESO 243-49. This suggests that HLX-1 is accreting gas related to its cluster's light-dominating young stars. Alternatively, the HLX-1 phenomenon could be so rare that no radio analog is expected in NGC 1023. Also, using a formalism heretofore applied to star clusters inmore » the Milky Way, the radio-luminosity upper limit for the massive-cluster stack corresponds to a 3σ IMBH mass of suggesting black hole mass fractions of.« less
Authors:
 [1] ;  [2] ;  [3]
  1. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
  2. Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands)
  3. International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia)
Publication Date:
OSTI Identifier:
22520124
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 150; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BLACK HOLES; GHZ RANGE; LUMINOSITY; MASS; MILKY WAY; RESOLUTION; SPACE; STAR ACCRETION; STAR CLUSTERS; STARS; TELESCOPES; VISIBLE RADIATION