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

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

    Research output: Contribution to journalArticlepeer-review

    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.
    Original languageEnglish
    Pages (from-to)395-433
    JournalNew Astronomy
    Volume7
    Issue number7
    DOIs
    Publication statusPublished - 2002

    Subject classification (UKÄ)

    • Astronomy, Astrophysics and Cosmology

    Free keywords

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

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