High-Resolution Infrared Spectra of Bulge Globular Clusters: Liller 1 and NGC 6553
High-Resolution Infrared Spectra of Bulge Globular Clusters: Liller 1 and NGC 6553
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球状球状星团的高分辨率红外光谱：Liller 1 和 NGC 6553
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
S. Castro
中科院分区：
文献类型：
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作者：
L. Origlia;R. Rich;S. Castro
我们利用凯克II望远镜上的NIRSPEC摄谱仪，获得了银河系核球中两颗最亮的巨星Liller 1和NGC 6553的阶梯光栅光谱，它们是银河系核球中古老的富金属球状星团。我们用光谱合成法进行丰度分析，发现两个星团中巨星的[Fe/H] = -0.3 ± 0.2，[O/H] = 0.3 ± 0.1（来自OH线）。我们测量了α元素Mg、Ca和Si的强谱线，但这些谱线对丰度的灵敏度较低，因此我们只能给出一般的[α/Fe] = 0.3 ± 0.2 dex。星团的组成类似于凸出部分的场星，并且与星团早期形成并迅速富集的情景相一致。我们很难用文献中最近报道的低值或高值来很好地拟合NGC 6553的光谱，除非分别采用非常大的α元素增强或不采用α元素增强。
Using the NIRSPEC spectrograph at Keck II, we have obtained echelle spectra covering the range 1.5–1.8 μm for two of the brightest giants in Liller 1 and NGC 6553, old metal-rich globular clusters in the Galactic bulge. We use spectrum synthesis for the abundance analysis and find [Fe/H] = -0.3 ± 0.2 and [O/H] = 0.3 ± 0.1 (from the OH lines) for the giants in both clusters. We measure strong lines for the α-elements Mg, Ca, and Si, but the lower sensitivity of these lines to abundance permits us only to state a general [α/Fe] = 0.3 ± 0.2 dex. The composition of the clusters is similar to that of field stars in the bulge and is consistent with a scenario in which the clusters formed early, with rapid enrichment. We have difficulty achieving a good fit to the spectrum of NGC 6553 using either the low or the high values recently reported in the literature, unless unusually large or no α-element enhancements are adopted, respectively.