A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc
A FIRST CONSTRAINT ON THE THICK DISK SCALE LENGTH: DIFFERENTIAL RADIAL ABUNDANCES IN K GIANTS AT GALACTOCENTRIC RADII 4, 8, AND 12 kpc
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DOI：
10.1088/2041-8205/735/2/l46
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发表时间：
2011-06
期刊：
影响因子：
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通讯作者：
T. Bensby;A. Alves-Brito;M. Oey;David Yong;Jorge Melendez
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作者：
T. Bensby;A. Alves-Brito;M. Oey;David Yong;Jorge Melendez
基于高分辨率光谱获得的MIKE摄谱仪的麦哲伦望远镜，我们提出了详细的元素丰度的20颗红巨星在银河系外盘，位于银心距离9和13千秒差距之间。外盘的样本补充了来自内银河系盘和太阳附近的红巨星样本，使用相同的方法进行分析。对于银心距离超过10千秒差距，我们只发现化学图案与当地薄盘，即使是远远高于银河平面的恒星。我们的结果表明，厚盘和薄盘的相对密度是显着不同的太阳附近，因此，我们建议厚盘的径向尺度长度比薄盘的短得多。我们首先估计厚盘尺度长度Lthick = 2.0 kpc，假设薄盘Lthin = 3.8 kpc。我们认为，径向迁移可以解释缺乏径向年龄，金属丰度，丰度梯度在厚盘，也可能解释厚盘和金属贫凸起之间的联系。
Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in the outer Galactic disk, located at Galactocentric distances between 9 and 13 kpc. The outer disk sample is complemented with samples of red giants from the inner Galactic disk and the solar neighborhood, analyzed using identical methods. For Galactocentric distances beyond 10 kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighborhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. We make a first estimate of the thick disk scale length of Lthick = 2.0 kpc, assuming Lthin = 3.8 kpc for the thin disk. We suggest that radial migration may explain the lack of radial age, metallicity, and abundance gradients in the thick disk, possibly also explaining the link between the thick disk and the metal-poor bulge.