Schedule Feb 17, 2012
The Chemical Signature of a Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Cosmology
Torgny Karlsson (Uppsala Univ.)

A relic star cluster in the Sextans Dwarf Spheroidal (dSph) is identified with the chemical tagging technique. At [Fe/H] = -2.7, it is currently the most metal-poor cluster known to have formed in the Universe. From a stochastic chemical evolution model of Sextans, we estimate the initial stellar mass of the cluster to M*,init = 1.9^+1.5_-0.9 (1.6^+1.2_-0.8) x 10^5 Msol, assuming a Salpeter (Kroupa) initial mass function (IMF). Inspired by this finding, we present a novel way of utilizing the ``chemical signatures'' of relic star clusters to study the process of star formation at the earliest times and probe the formation of the first galaxies in the universe. A comparison with avalilable data suggests that the newly discovered ultra-faint dwarf galaxies and the dSphs may be of different origin.


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