论文标题

球状簇和田间星星的高分辨率近红外光谱朝向银河凸起

High-resolution near-infrared spectroscopy of globular cluster and field stars toward the Galactic bulge

论文作者

Lim, Dongwook, Koch-Hansen, Andreas J., Chun, Sang-Hyun, Hong, Seungsoo, Lee, Young-Wook

论文摘要

球状簇(GC)在银河系的形成和演变中起着重要作用。不断发现新的候选者,特别是在凸起的高纬度低纬度区域中,尽管它们的存在和特性尚未得到验证。为了调查新的GC候选者,我们使用双子座南南望远镜的Igrins仪器对恒星进行了高分辨率NIR光谱。我们分别在Camargo 1103和1106附近选择了15颗和10颗星,最近据报道是凸起的金属贫困GC候选者。与光谱法中使用的经典方法相反,我们从线深度比和CO线的等效宽度的组合确定了恒星参数。恒星的恒星参数遵循附近宇宙恒星的共同趋势。我们还通过频谱合成确定了Fe,Na,Mg,al,S,K,Ca,Ti,Cr,Ni和CE的丰度。没有明确的证据表明在RV- [Fe/H]空间中进行分组,这表明将任何一个物体作为金属贫困GC的表征。该结果强调了新的GC候选者朝向凸起的随访光谱的必要性,尽管我们不能完全排除我们只观察到非会员恒星的低概率。我们还注意到,源自H-k and k频段光谱时,Al,CA和Ti的丰度之间存在差异。尽管这种差异的原因尚不清楚,但讨论了大气参数或NLTE的影响。我们的方法和结果表明,IGRINS光谱是一种有用的工具,用于研究恒星向银河凸起的化学特性,其统计不确定性为0.03 DEX的统计不确定性,而通过大气参数的不确定性,系统误差略大于光谱中的测量值。

Globular clusters (GCs) play an important role in the formation and evolution of the Milky Way. New candidates are continuously found, particularly in the high-extinction low-latitude regions of the bulge, although their existence and properties have yet to be verified. In order to investigate the new GC candidates, we performed high-resolution NIR spectroscopy of stars toward the bulge using the IGRINS instrument at the Gemini-South telescope. We selected 15 and 10 stars near Camargo 1103 and 1106, respectively, which have recently been reported as metal-poor GC candidates in the bulge. In contrast to the classical approaches used in optical spectroscopy, we determined stellar parameters from a combination of line-depth ratios and the equivalent width of a CO line. The stellar parameters of the stars follow the common trends of nearby APOGEE stars in a similar magnitude range. We also determined the abundances of Fe, Na, Mg, Al, Si, S, K, Ca, Ti, Cr, Ni, and Ce through spectrum synthesis. There is no clear evidence of a grouping in RV-[Fe/H] space that would indicate the characterization of either object as metal-poor GCs. This result emphasizes the necessity of follow-up spectroscopy for new GC candidates toward the bulge, although we cannot completely rule out a low probability that we only observed nonmember stars. We also note discrepancies between the abundances of Al, Ca, and Ti when derived from the H- vs. the K-band spectra. Although the cause of this discrepancy is not clear, the effects of atmosphere parameters or NLTE are discussed. Our approach and results demonstrate that IGRINS spectroscopy is a useful tool for studying the chemical properties of stars toward the Galactic bulge with a statistical uncertainty in [Fe/H] of 0.03 dex, while the systematic error through uncertainties of atmospheric parameter is slightly larger than in measurements from optical spectroscopy.

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