红外望远镜设施（IRTF）光谱库II：Y、J、H和L大气窗口中的新指数
Infrared Telescope Facility (IRTF) spectral library II: New indices in Y, J, H, and L atmospheric windows
摘要：
红外波段的恒星星族研究在光学方面有两个主要优势：它们探测不同的恒星族，因为红外波段的大部分光来自较红且通常较老的恒星;它们使我们能够透过尘埃看到，因为红外光受消光的影响较小。不幸的是，由于缺乏足够的恒星库，IR建模工作停止了，但近年来这种情况已经改变。我们的项目研究了1- 5 μ m波长范围内的各种光谱特征对恒星物理性质（$μ$，[Fe/H]，log g）的敏感性，目的是客观地定义光谱指数，以表征未分辨恒星星族的年龄和金属丰度。我们实现了一种方法，该方法使用指数的导数作为$T_{eff}$，[Fe/H]或log g的函数，在整个可用的波长范围内，以揭示对这些参数最敏感的指数以及这些指数工作的范围。在这里，我们补充了以前的工作在I和K波段，报告了一个新的系统的14，12，22和12指数的Y，J，H和L大气窗口，分别，并描述其行为。我们的分析表明，有效温度敏感的功能是存在的，可测量的光谱分辨率和IRTF库的金属丰度范围内的所有调查的大气窗口的信噪比大于20-30。表面重力更具挑战性，只有H和J窗口中的指数最适合于此。可用光谱的恒星的金属丰度范围太窄，无法进行适当的诊断。对于未分辨星系的光谱，定义的指数是追踪红外优势恒星星族中恒星性质的有价值的工具。
英文摘要：
Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in the IR comes from redder and generally older stars, and they allow us to see through dust because IR light is less affected by extinction. Unfortunately, IR modeling work was halted by the lack of adequate stellar libraries, but this has changed in the recent years. Our project investigates the sensitivity of various spectral features in the 1--5\,$μ$m wavelength range to the physical properties of stars ($T_{eff}$, [Fe/H], log g and aims to objectively define spectral indices that can characterize the age and metallicity of unresolved stellar populations. We implemented a method that uses derivatives of the indices as functions of $T_{eff}$, [Fe/H] or log g across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work. Here, we complement the previous work in the I and K bands, reporting a new system of 14, 12, 22, and 12 indices for Y, J, H, and L atmospheric windows, respectively, and describe their behavior. Our analysis indicates that features sensitive to the effective temperature are present and measurable in all the investigated atmospheric windows at the spectral resolution and in the metallicity range of the IRTF library for a signal-to-noise ratio greater than 20-30. The surface gravity is more challenging and only indices in the H and J windows are best suited for this. The metallicity range of the stars with available spectra is too narrow to search for suitable diagnostics. For the spectra of unresolved galaxies, the defined indices are valuable tools in tracing the properties of the stars in the IR-dominant stellar populations.
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