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A Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Early Star and Galaxy Formation
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
2012 (English)In: Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way, 2012, Vol. 458Conference paper (Refereed)
Abstract [en]

We present tentative evidence for the existence of a dissolved star cluster in the Sextans dwarf spheroidal galaxy. In a sample of six stars, we identify three (possibly four) stars around [Fe/H] = -2.7 that are highly clustered in a multi-dimensional chemical abundance space. The estimated initial stellar mass of the cluster is M$_*,init$ = 1.9$^+1.5$$_-0.9$ (1.6$^+1.2$$_-0.8$)\times 10$^5$ M$_&sun;$ assuming a Salpeter (Kroupa) initial mass function (IMF). If corroborated by follow-up spectroscopy, this ancient star cluster at [Fe/H] = -2.7 is the most metal-poor system identified to date. Inspired by this finding, we also present a new way to interpret the cumulative metallicity functions of dwarf galaxies. From available observational data, we speculate that the ultra-faint dwarf galaxy population, or a significant fraction thereof, and the more luminous, classical dwarf spheroidal population were formed in different environments and would thus be distinct in origin.

Place, publisher, year, edition, pages
2012. Vol. 458
, Astronomical Society of the Pacific Conference Series
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-196839OAI: oai:DiVA.org:uu-196839DiVA: diva2:610956
Astronomical Society of the Pacific Conference
Available from: 2013-03-13 Created: 2013-03-13 Last updated: 2013-03-13

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