THE FRACTIONS OF INNER- AND OUTER-HALO STARS IN THE LOCAL VOLUME
THE FRACTIONS OF INNER- AND OUTER-HALO STARS IN THE LOCAL VOLUME
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DOI：
10.1088/2041-8205/813/2/l28
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
D. An;T. Beers;Rafael M. Santucci;D. Carollo;V. Placco;Y. S. Lee;S. Rossi
中科院分区：
文献类型：
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作者：
D. An;T. Beers;Rafael M. Santucci;D. Carollo;V. Placco;Y. S. Lee;S. Rossi
基于最近改进的Sloan数字巡天Stripe 82的ugriz光度学的联合增加，我们获得了一个新的测定太阳105 -10 kpc范围内恒星的金属丰度分布函数。我们的新估计使用了An等人以前开发的方法来研究原位晕星，但基于比以前大两倍的样本，并大大改善了光度误差和零点。新获得的日冕可以分为多个晕星群体，峰值金属丰度为[Fe/H]<$-1.4和1.9，我们分别将其与银河系的内晕和外晕群体联系起来。我们发现，这些恒星的运动学（基于在银河系高纬度的自行测量）支持所提出的二分法的晕，因为在银河系的休息帧逆行运动的恒星通常是更少的金属比恒星的逆运动，与以前的索赔。此外，我们产生模拟目录的恒星从模拟牛奶路晕系统，并证明了第一次的化学和运动学上不同的性质的内晕和外晕人口定性与我们的观察。观察到的MDF的分解以及我们与模拟目录结果的比较表明，外晕种群对局部体积中晕星的贡献约为35%-55%。
We obtain a new determination of the metallicity distribution function (MDF) of stars within ∼5–10 kpc of the Sun, based on recently improved co-adds of ugriz photometry for Stripe 82 from the Sloan Digital Sky Survey. Our new estimate uses the methodology developed previously by An et al. to study in situ halo stars, but is based on a factor of two larger sample than available before, with much-improved photometric errors and zero-points. The newly obtained MDF can be divided into multiple populations of halo stars, with peak metallicities at [Fe/H] ≈ −1.4 and −1.9, which we associate with the inner-halo and outer-halo populations of the Milky Way, respectively. We find that the kinematics of these stars (based on proper-motion measurements at high Galactic latitude) supports the proposed dichotomy of the halo, as stars with retrograde motions in the rest frame of the Galaxy are generally more metal-poor than stars with prograde motions, consistent with previous claims. In addition, we generate mock catalogs of stars from a simulated Milk Way halo system, and demonstrate for the first time that the chemically and kinematically distinct properties of the inner- and outer-halo populations are qualitatively in agreement with our observations. The decomposition of the observed MDF and our comparison with the mock catalog results suggest that the outer-halo population contributes on the order of ∼35%–55% of halo stars in the local volume.