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arXiv 1202.1304astro-ph.GA
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银河系球状星团的均匀金属丰度和径向速度

Homogeneous Metallicities and Radial Velocities for Galactic Globular Clusters

Ivo Saviane, Gary S. Da Costa, Enrico V. Held, Veronica Sommariva, Marco Gullieuszik, Beatriz Barbuy, Sergio Ortolani

摘要:

确定径向速度和丰度是分析银河系球状星团系统性质的基础。然而,超过50%的这些集群没有光谱测量其金属丰度。在这种情况下,这项工作提供了新的径向速度和丰度的20个银河系球状星团,缺乏或有很少知道这些数量的值。径向速度和丰度来自于使用VLT的FORS 2成像仪和摄谱仪在Ca II三重态获得的光谱,并使用许多具有良好丰度的星团中的红巨星光谱进行校准。对于我们样本中大约一半的星系团,我们对现有的速度或丰度,或两者都进行了重大修订。我们还确认了位于人马座矮星系中心的球状星团M54中存在相当大的丰度分布。此外,在明亮的遥远球状星团NGC 5824中,还存在一个小的内部丰度分布(σ [Fe/H](int)~ 0.11-0.14 dex,类似于M54)。因此,这个星团加入了少数已知具有内部金属丰度([Fe/H])分布的银河系球状星团。

英文摘要:

Well determined radial velocities and abundances are essential for analyzing the properties of the Globular Cluster system of the Milky Way. However more than 50% of these clusters have no spectroscopic measure of their metallicity. In this context, this work provides new radial velocities and abundances for twenty Milky Way globular clusters which lack or have poorly known values for these quantities. The radial velocities and abundances are derived from spectra obtained at the Ca II triplet using the FORS2 imager and spectrograph at the VLT, calibrated with spectra of red giants in a number of clusters with well determined abundances. For about half of the clusters in our sample we present significant revisions of the existing velocities or abundances, or both. We also confirm the existence of a sizable abundance spread in the globular cluster M54, which lies at the center of the Sagittarius dwarf galaxy. In addition evidence is provided for the existence of a small intrinsic internal abundance spread (sigma [Fe/H](int) ~ 0.11-0.14 dex, similar to that of M54) in the luminous distant globular cluster NGC 5824. This cluster thus joins the small number of Galactic globular clusters known to possess internal metallicity ([Fe/H]) spreads.

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