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

Dennis Zaritsky, Janet E. Colucci, Peter M. Pessev, Rebecca A. Bernstein, Rupali Chandar

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


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, Υ, of the high and low Υ cluster populations are well-matched to those found in recent studies of early and late type galaxies, respectively.

Original languageEnglish (US)
Article number71
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 1 2014


  • galaxies: evolution
  • galaxies: stellar content
  • stars: formation
  • stars: luminosity function, mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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