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

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Author

  • RFG Wyse
  • G Gilmore
  • ML Houdashelt
  • Sofia Feltzing
  • L Hebb
  • JS Gallagher
  • TA Smecker-Hane

Summary, in English

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.

Publishing year

2002

Language

English

Pages

395-433

Publication/Series

New Astronomy

Volume

7

Issue

7

Document type

Journal article

Publisher

Elsevier

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • individual : Ursa Minor
  • mass function
  • stars : luminosity function
  • dark matter
  • galaxies : stellar content
  • kinematics and dynamics
  • galaxies :

Status

Published

ISBN/ISSN/Other

  • ISSN: 1384-1092