Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems
Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems
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银河核球场红巨星中的锌丰度：对阻尼莱曼-α系统的影响
DOI：
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发表时间：
2015
期刊：
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通讯作者：
A. Gómez
中科院分区：
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作者：
B.Barbuy;A. Friaça;C. Silveira;V. Hill;M. Zoccali;D. Minniti;A. Renzini;S. Ortolani;A. Gómez
上下文恒星中的锌是一个重要的参考元素，因为它在阻尼莱曼-α系统（DLAs）的研究中是Fe的替代物，允许比较核球恒星种群和DLAs的化学演化历史。在核合成方面，它表现为α元素，因为它在贫金属恒星中得到增强。对不同星族的近红外光谱研究可以提供不同地点Zn产生的线索。目标。本工作的目的是从高分辨光谱中获得56颗球巨星的铁峰元素Zn丰度。为了更好地理解这些环境中的化学演化，将这些结果与其他核球样品、盘星和晕星以及阻尼莱曼-α系统的数据进行了比较。方法.在甚大望远镜上使用FLAMES+UVES获得了高分辨率光谱。我们利用4810.53和6362.34 A处的Zn i线计算了Zn的丰度。我们考虑了Zn i 6362.34 A线连续谱中的强压低，这是由于Ca i 6361.79 A线的两翼遭受自电离而引起的。计算中还包括混合Zn 16362.34 A线的CN线。结果我们发现在−1.3 < [Fe/H] < −0的范围内，[Zn/Fe] =+0.24 ± 0.02。在−0.5 < [Fe/H] < −0.1的范围内，[Zn/Fe] =+ 0.06 ± 0.02，而在[Fe/H] ≥− 0.1的范围内，[Zn/Fe]的分布为−0.60 < [Zn/Fe] <+0.15，其中大部分恒星的[Zn/Fe] < 0.0。这些低锌丰度在高金属量端的凸起定义了一个下降的趋势[Zn/Fe]与金属量的增加。与锌丰度DLA系统的比较，其中灰尘贫化校正适用于锌和铁。当我们考虑这些修正时，DLAs的[Zn/Fe]与[Fe/H]落在与厚盘和凸起恒星相同的区域。最后，我们提出了一个化学演化模型的Zn富集在大规模的球体，代表了一个典型的经典的隆起演化。
Context. Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-α systems (DLAs), permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. Abundance studies in different stellar populations can give hints to the Zn production in different sites. Aims. The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-α systems, in order to better understand the chemical evolution in these environments. Methods. High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We computed the Zn abundances using the Zn i lines at 4810.53 and 6362.34 A. We considered the strong depression in the continuum of the Zn i 6362.34 A line, which is caused by the wings of the Ca i 6361.79 A line suffering from autoionization. CN lines blending the Zn i 6362.34 A line are also included in the calculations. Results. We find [Zn/Fe] =+ 0.24 ± 0.02 in the range −1.3 < [Fe/H] < −0. 5a nd [Zn/Fe] =+ 0.06 ± 0.02 in the range −0.5 < [Fe/H] < −0.1, whereas for [Fe/H] ≥− 0.1, it shows a spread of −0.60 < [Zn/Fe] < +0.15, with most of these stars having low [Zn/Fe] < 0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. When we take these corrections into account, the [Zn/Fe] vs. [Fe/H] of the DLAs fall in the same region as the thick disk and bulge stars. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge evolution.