Evidence for two distinct stellar initial mass functions: Revisiting the effects of cluster dynamical evolution

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

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We measure the velocity dispersions of six galactic globular clusters using spatially integrated spectra, to test for the effects of internal dynamical evolution in the stellar mass-to-light ratios, Υ*, of star clusters. In particular, we revisit whether the low values of Υ* that we found in our previous study, from which we concluded that there are at least two population of stellar clusters with distinct stellar initial mass functions, are artificially depressed by relaxation driven mass loss. The combination of our previous sample of five old clusters and these six now provide an order of magnitude range in cluster mass with which to explore this issue. We find no relationship between cluster mass, or relaxation time, and Υ*. Because relaxation is mass dependent, we conclude that the values of Υ* for these clusters are not strongly affected by dynamical effects, and so confirm the presence of the population of clusters with low Υ*.

Original languageEnglish (US)
Article number121
JournalAstrophysical Journal
Issue number2
StatePublished - Jun 20 2013



  • galaxies: evolution
  • galaxies: fundamental parameters
  • stars: formation
  • stars: luminosity function, mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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