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arXiv · 0810.4353

The Age and Metallicity of the Bootes I System

Joanne Hughes·George Wallerstein·Anne Bossi
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Abstract

We present Washington photometry of a field central to the Bootes I dwarf spheroidal galaxy, which was discovered as a stellar overdensity in the Sloan Digital Sky Survey (DR5). We show that the Washington filters are much more effective than the Sloan filters in separating the metal-poor turn-off stars in the dwarf galaxy from the foreground stars. We detect 165 objects in the field, and statistically determine that just over 40% of the objects are non-members. Our statistical analysis mostly agrees with radial velocity measurements of the brighter stars. We find that that there is a distinct main-sequence turn-off and subgiant branch, where there is some evidence of a spread in chemical abundance. Any evidence of an age spread is limited to a few billion years. The brightest 7 Bootes I members give a (photometric-color derived) weighted mean iron-abundance of [Fe/H]=-2.1+/-0.4, and the best-fit isochrone is the 14.1 Gyr, Z=0.0002 model, with DM=19.11 and E(B-V)=0.02.

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Joanne Hughes, George Wallerstein, Anne Bossi. 2008-10-23. The Age and Metallicity of the Bootes I System. https://doi.org/10.1088/0004-6256%2F136%2F6%2F2321

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