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The chemical signature of a relic star cluster in the sextans dwarf spheroidal galaxy: Implications for near-field cosmology
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
2012 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 759, no 2, 111- p.Article in journal (Refereed) Published
Abstract [en]

We present tentative evidence for the existence of a dissolved star cluster at [Fe/H] = -2.7 in the Sextans dwarf spheroidal galaxy. We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space (-space). In a sample of six stars, three, possibly four, stars are identified as potential cluster stars. The initial stellar mass of the parent cluster is estimated from two independent observations to be , assuming a Salpeter (Kroupa) initial mass function. If corroborated by follow-up spectroscopy, this star cluster is the most metal-poor system identified to date. Chemical signatures of remnant clusters in dwarf galaxies like Sextans provide us with a very powerful probe to the high-redshift universe. From available observational data, we argue that the average star cluster mass in the majority of the newly discovered ultra-faint dwarf galaxies was notably lower than it is in the Galaxy today and possibly lower than in the more luminous, classical dwarf spheroidal galaxies. Furthermore, the mean cumulative metallicity function of the dwarf spheroidals falls below that of the ultra-faints, which increases with increasing metallicity as predicted from our stochastic chemical evolution model. These two findings, together with a possible difference in the 〈[Mg/Fe]〉 ratio suggest that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the dwarf spheroidal population were formed in different environments and would thus be distinct in origin.

Place, publisher, year, edition, pages
2012. Vol. 759, no 2, 111- p.
Keyword [en]
galaxies, dwarf, galaxies, formation, galaxies, star clusters, general, Galaxy, formation, stars, abundances, stars, Population II
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-184906DOI: 10.1088/0004-637X/759/2/111ISI: 000310911300034OAI: oai:DiVA.org:uu-184906DiVA: diva2:570763
Available from: 2012-11-20 Created: 2012-11-15 Last updated: 2013-03-13Bibliographically approved

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Karlsson, Torgny
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