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Mg abundances in metal-poor halo stars as a tracer of early Galactic mixing

Arnone, E.; Ryan, S. G.; Argast, D.; Norris, J. E. and Beers, T. C. (2005). Mg abundances in metal-poor halo stars as a tracer of early Galactic mixing. Astronomy and Astrophysics, 430(2) pp. 507–522.

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We present results of a detailed chemical analysis performed on 23 main-sequence turnoff stars having - 3.4 less than or equal to [Fe/H] less than or equal to - 2.2, a sample selected to be highly homogeneous in T-eff and log(g). We investigate the efficiency of mixing in the early Galaxy by means of the [Mg/Fe] ratio, and find that all values lie within a total range of 0.2 dex, with a standard deviation about the mean of 0.06 dex, consistent with measurement errors. This implies there is little or no intrinsic scatter in the early ISM, as suggested also by the most recent results from high-quality VLT observations. These results are in contrast with inhomogeneous Galactic chemical evolution (iGCE) models adopting present supernova (SN) II yields, which predict a peak-to-peak scatter in [Mg/Fe] as high as 1 dex at very low metallicity, with a corresponding standard deviation of about 0.4 dex. We propose that cooling and mixing timescales should be investigated in iGCE models to account for the apparent disagreement with present observations. The contrast between the constancy and small dispersion of [Mg/Fe] reported here and the quite different behaviour of [Ba/Fe] indicates, according to this interpretation, that Mg and Ba are predominantly synthesised in different progenitor mass ranges.

Item Type: Journal Article
Copyright Holders: ESO 2005
ISSN: 1432-0746
Academic Unit/Department: ?? scie-phya ??
Item ID: 18429
Depositing User: Colin Smith
Date Deposited: 28 Sep 2009 13:35
Last Modified: 19 Feb 2012 20:54
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