Near-infrared photometry of globular clusters towards the Galactic bulge: observations and photometric metallicity indicators
Near-infrared photometry of globular clusters towards the Galactic bulge: observations and photometric metallicity indicators
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DOI：
10.1093/mnras/stw2435
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发表时间：
2016-09
影响因子：
4.8
通讯作者：
R. Cohen;C. M. Bidin;F. Mauro;C. Bonatto;Douglas Geisler Universidad de Concepcion;Universidad Cat'olica del Norte-Universida
中科院分区：
文献类型：
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作者：
R. Cohen;C. M. Bidin;F. Mauro;C. Bonatto;Douglas Geisler Universidad de Concepcion;Universidad Cat'olica del Norte-Universida
本文介绍了在2 MASS测光系统上标定的16个银河系球状星团的宽视场JHKs测光。差分红化校正和统计领域的星星净化之前，所有这些集群拟合基准序列的集群红巨星分支（RGBs）。观察值和不确定性报告的几个光度特征，包括RGB凹凸，尖端，水平分支（HB）和上RGB的斜率的大小。最新的光谱测定的化学丰度被用来建立距离和红独立的关系观察到的光度特征和集群金属，优化样本大小和金属基线这些关系的补充我们的样本与文献中的结果。我们发现，HB和RGB凸点之间的幅度差异可以用来预测金属丰度，在铁丰度[Fe/H]和全球金属丰度[M/H]方面，在所有三个近红外带通相对富含金属（[M/H]$\gtrsim$-1）集群的精度优于0.1德克斯。与此同时，上RGB的斜率和RGB尖端与凸起之间的幅度差异都是整个采样金属丰度范围（-2\lesssim$0）内有用的金属丰度指标，精度为0.2 dex或更好，尽管模型预测RGB斜率在高（近太阳）金属丰度时可能变得不可靠。我们的研究结果同意与以前的校准，根据相关的不确定性，我们讨论了有争议的金属丰度集群的影响，以及进一步调查的方向。
We present wide field JHKs photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the 2MASS photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature. We find that the magnitude different between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relative metal-rich ([M/H]$\gtrsim$-1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2$\lesssim$[M/H]$\lesssim$0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.