Faint stars in the Ursa Minor dwarf spheroidal galaxy: implications for the low-mass stellar initial mass function at high redshift

R F G Wyse, G Gilmore, M L Houdashelt, S Feltzing, L Hebb, J S Gallagher, T A Smecker-Hane

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

The stellar initial mass function at high redshift is an important defining property of the first stellar systems to form and may also play a role in various dark matter problems. We here determine the faint stellar luminosity function in an apparently dark-matter-dominated external galaxy in which the stars formed at high redshift. The Ursa Minor dwarf spheroidal galaxy is a system with a particularly simple stellar population-all of the stars being old and metal-poor-similar to that of a classical halo globular cluster. A direct comparison of the faint luminosity functions of the UMi dSph and of similar metallicity, old globular clusters is equivalent to a comparison of the initial mass functions and is presented here, based on deep HST WFPC2 and STIS imaging data. We find that these luminosity functions are indistinguishable, down to a luminosity corresponding to similar to0.3 M-.. Our results show that the low-mass stellar IMF for stars that formed at very high redshift is apparently invariant across environments as diverse as those of an extremely low-surface-brightness, dark-matter-dominated dwarf galaxy and a dark-matter-free, high-density globular cluster within the Milky Way. (C) 2002 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)395-433
Number of pages39
JournalNew Astronomy
Volume7
Issue number7
DOIs
Publication statusPublished - Oct 2002

Keywords

  • stars : luminosity function, mass function
  • dark matter
  • galaxies : individual : Ursa Minor
  • galaxies : stellar content
  • galaxies : kinematics and dynamics
  • TELESCOPE IMAGING SPECTROGRAPH
  • HST LUMINOSITY FUNCTIONS
  • ON-ORBIT PERFORMANCE
  • GLOBULAR-CLUSTERS
  • GALACTIC BULGE
  • DARK-MATTER
  • CHEMICAL EVOLUTION
  • FORMATION HISTORY
  • BLUE-STRAGGLERS
  • ELEMENT RATIOS

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