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Title: Evidence for two distinct stellar initial mass functions: probing for clues to the dichotomy

We present new measurements of the velocity dispersions of 11 Local Group globular clusters using spatially integrated spectra, to expand our sample of clusters with precise integrated-light velocity dispersions to 29, over 4 different host galaxies. This sample allows us to further our investigation of the stellar mass function among clusters, with a particular emphasis on a search for the driver of the apparent bimodal nature of the inferred stellar initial mass function (IMF). We confirm our previous result that clusters fall into two classes. If, as we argue, this behavior reflects a variation in the stellar IMF, the cause of that variation is not clear. The variations do not correlate with formation epoch as quantified by age, metallicity quantified by [Fe/H], host galaxy, or internal structure as quantified by velocity dispersion, physical size, relaxation time, or luminosity. The stellar mass-to-light ratios, Y{sub *}, of the high and low Y{sub *} cluster populations are well-matched to those found in recent studies of early and late type galaxies, respectively.
Authors:
 [1] ; ;  [2] ;  [3] ;  [4]
  1. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  2. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  3. Gemini South Observatory, c/o AURA Inc., Casilla 603, La Serena (Chile)
  4. Department of Physics and Astronomy, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States)
Publication Date:
OSTI Identifier:
22370181
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DISPERSIONS; GALAXIES; LUMINOSITY; MASS; METALLICITY; RELAXATION TIME; SPECTRA; STAR CLUSTERS; STAR EVOLUTION; STARS; VELOCITY; VISIBLE RADIATION