Insights from the outskirts: Chemical and dynamical properties in the outer parts of the Fornax dwarf spheroidal galaxy
Insights from the outskirts: Chemical and dynamical properties in the outer parts of the Fornax dwarf spheroidal galaxy
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来自郊区的见解：天炉座矮椭球星系外部的化学和动力学特性
DOI：
10.1051/0004-6361/201424645
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发表时间：
2014
影响因子：
6.5
通讯作者：
G. Gilmore
中科院分区：
文献类型：
--
作者：
B. Hendricks;A. Koch;M. Walker;Christian I. Johnson;J. Peñarrubia;G. Gilmore
本文给出了340颗天炉座矮椭球体R = 16000的径向速度和[Fe/H]丰度。这些目标是在星系的外部获得的，这是一个研究很少的区域。我们的样品显示[Fe/H]范围很宽，介于-0。5a nd-3.0 dex，其中我们检测到三个子群。去除属于最富金属人口的恒星产生截断的金属丰度分布函数，这是相同的玉夫座，表明这些系统共享一个类似的早期演化，除了天炉座经历了后期，强烈的星星形成（SF）。导出的年龄-金属丰度关系表明，[Fe/H]在早期快速增加，之后的富集显着的年轻于108 Gyr的恒星。此外，数据显示在4 Gyr附近有一个强大的恒星群体，然后是[Fe/H]的第二次快速富集。一个漏盒化学富集模型通常与观测到的关系相匹配，但既没有预测到大量的年轻恒星，也没有预测到后期的强烈富集。因此，天炉座的年轻人口可能源于外部触发的SF事件。我们的动力学分析表明，随着[Fe/H]的降低，速度分散度增加。5k m s −1至≥14 km s −1。在低金属丰度下的大速度色散可能是年龄大于108 Gyr的恒星的非高斯速度分布的结果。我们的样本还包括来自天炉座球状星团H2和H5的成员。与过去的研究一致，我们发现H2的[Fe/H] = −2.04 ± 0.04，平均径向速度RV = 59.36 ± 0.31 km s −1; H5的[Fe/H] = −2.02 ± 0.11，RV = 59.39 ± 0.44 km s −1。最后，我们在[Fe/H]中测试了超过2 dex的钙三重态的不同校准，并发现与Carrera等人（2013，MNRAS，434，1681）提供的校准方程最吻合。总的来说，我们发现化学和动力学性质的高度复杂性，签名还随银河系距离而变化。因此，我们需要详细了解恒星在所有半径上的性质，才能对天炉座的星星形成和化学演化做出结论性的描述。
We present radial velocities and [Fe/H] abundances for 340 stars in the Fornax dwarf spheroidal from R ∼ 16 000 spectra. The targets were obtained in the outer parts of the galaxy, a region that has been poorly studied. Our sample shows a wide range in [Fe/H], between −0. 5a nd−3.0 dex, in which we detect three subgroups. Removal of stars belonging to the most metal-rich population produces a truncated metallicity distribution function that is identical to Sculptor, indicating that these systems shared a similar early evolution, except that Fornax experienced a late, intense period of star formation (SF). The derived age-metallicity relation shows a fast increase in [Fe/H] at early ages, after which the enrichment flattens significantly for stars younger than ∼8 Gyr. Additionally, the data indicate a strong population of stars around 4 Gyr, followed by a second rapid enrichment in [Fe/H]. A leaky-box chemical enrichment model generally matches the observed relation but predicts neither a significant population of young stars nor strong enrichment at late times. The young population in Fornax may therefore stem from an externally triggered SF event. Our dynamical analysis reveals an increasing velocity dispersion with decreasing [Fe/H] from σsys ≈ 7. 5k m s −1 to ≥14 km s −1 . The large velocity dispersion at low metallicities is possibly the result of a non-Gaussian velocity distribution among stars older than ∼8 Gyr. Our sample also includes members from the Fornax globular clusters H2 and H5. In agreement with past studies we find [Fe/H] = −2.04 ± 0.04 and a mean radial velocity RV = 59.36 ± 0.31 km s −1 for H2 and [Fe/H] = −2.02 ± 0.11 and RV = 59.39 ± 0.44 km s −1 for H5. Finally, we test different calibrations of the calcium triplet over more than 2 dex in [Fe/H] and find best agreement with the calibration equations provided by Carrera et al. (2013, MNRAS, 434, 1681). Overall, we find high complexity in the chemical and dynamical properties, with signatures that additionally vary with galactocentric distance. Detailed knowledge about the properties of stars at all radii is therefore needed to draw a conclusive picture about the star formation and chemical evolution in Fornax.
穹窿矮球状星系中贫金属的膝盖
DOI：
10.1088/0004-637x/785/2/102
发表时间：
2014
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Hendricks;Lanfranchi;Boeche;Walker;Johnson;Peñarrubia;Gilmore
通讯作者：
Gilmore