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

被引:74
作者
Arnone, E [1 ]
Ryan, SG
Argast, D
Norris, JE
Beers, TC
机构
[1] Open Univ, Dept Phys & Astron, Milton Keynes MK7 6AA, Bucks, England
[2] Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England
[3] Univ Basel, Dept Phys & Astron, Basel, Switzerland
[4] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia
[5] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[6] Michigan State Univ, JINA, E Lansing, MI 48824 USA
关键词
stars : Population II; stars : abundances; Galaxy : formation; Galaxy : evolution; Galaxy : halo;
D O I
10.1051/0004-6361:20041034
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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.
引用
收藏
页码:507 / U61
页数:19
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