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 language | English |
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Pages (from-to) | 395-433 |
Number of pages | 39 |
Journal | New Astronomy |
Volume | 7 |
Issue number | 7 |
DOIs | |
Publication status | Published - 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