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arXiv · 1202.3815

A Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Early Star and Galaxy Formation

Torgny Karlsson·Joss Bland-Hawthorn
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Abstract

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)*10^5 Msol 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.

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Torgny Karlsson, Joss Bland-Hawthorn. 2012-02-16. A Relic Star Cluster in the Sextans Dwarf Spheroidal Galaxy - Implications for Early Star and Galaxy Formation. https://arxiv.org/abs/1202.3815

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