球状星团NGC 3115在近红外波段。证明两种对立情景的正确性
Globular clusters of NGC 3115 in the near-infrared. Demonstrating the correctness of two opposing scenarios
摘要:
我们结合新的近红外VLT/HAWK-I数据的球状星团(GC)在孤立的边缘上的S 0星系NGC 3115的光学和光谱从文献中获取的,目的是分析多波段GC颜色分布。SLUGGS巡天最近的一项研究表明,该星系中的GC遵循Ca II三重态指数的双峰分布。因此,NGC 3115提出了一个具有多个不同金属丰度亚群的GC系统的关键例子,这可能会反对“投影”方案,该方案假定普遍存在的颜色双峰性主要是由颜色-金属丰度关系中的非线性引起的。使用光学,近红外光谱和光谱数据,我们发现了强有力的和一致的证据,指数双峰,独立地证实了NGC 3115 GC中的金属丰度双峰。同时,我们也发现了一些颜色-颜色非线性的证据。在以前研究的更广泛背景下,NGC 3115中GC双峰的一致性表明,在GC系统的光学和光学-近红外颜色分布之间存在明显差异的情况下(如在一些巨型椭圆星系中),明显的不一致性很可能是由颜色-金属丰度关系的非线性引起的。
英文摘要:
We combined new near-infrared VLT/HAWK-I data of the globular clusters (GCs) in the isolated edge-on S0 galaxy NGC 3115 with optical and spectroscopic ones taken from the literature, with the aim of analyzing the multiband GC color distributions. A recent study from the SLUGGS survey has shown that the GCs in this galaxy follow a bimodal distribution of Ca II triplet indices. Thus, NGC 3115 presents a critical example of a GC system with multiple, distinct, metallicity subpopulations, and this may argue against the "projection" scenario, which posits that the ubiquitous color bimodality mainly results from nonlinearities in the color-metallicity relations. Using optical, NIR, and spectroscopic data, we found strong and consistent evidence of index bimodality, which independently confirms the metallicity bimodality in NGC 3115 GCs. At the same time, we also found evidence for some color-color nonlinearity. Taken in the broader context of previous studies, the multicolor consistency of the GC bimodality in NGC 3115 suggests that in cases where GC systems exhibit clear differences between their optical and optical-NIR color distributions (as in some giant ellipticals), the apparent inconsistencies most likely result from nonlinearities in the color-metallicity relations.
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