在SDSS和IDS光谱分辨率下[ M/H ] 0.0到-6.0红巨星的NLTE和LTE Lick指数
NLTE and LTE Lick indices for red giants from [M/H] 0.0 to -6.0 at SDSS and IDS spectral resolution
摘要：
我们研究了22个Lick指数的完整系统对从太阳丰度[M/H]标度的总金属丰度的依赖性，对于晚型巨星，从太阳值0.0到极贫金属（XMP）值-6.0（MK光度等级III，log（g）=2.0），属于MK光谱等级late-K到late-F（3750 < Teff < 6500 K）的类型，在星系晕和河外结构中被探测为早期星系形成的“化石”。我们的调查是基于合成指数值，I，来自大气模型和合成光谱计算与PHOENIX在LTE和非LTE（NLTE），其中合成光谱已卷积的光谱分辨率，R，IDS和SDSS（和LAMOST）光谱。我们确定了九个指数，我们命名为“Lick-XMP”，它们在至少~-5.0的[M/H]值下保持可检测和显著的[M/H]依赖性，并且在五种情况下降低到[M/H] ~ -6.0，同时也保持良好的行为。对于这九个，我们研究的依赖性，我对NLTE的影响，和光谱分辨率。对于SDSS分辨率光谱的LTEI值，我们给出了拟合多项式系数C_n，它来自于自变量对（Teff，[M/H]）和（V-K，[M/H]）中项最高达三阶的I的多元线性回归，并将它们与Worthey等人（1994）在IDS光谱分辨率下的拟合C_n值进行了比较。
英文摘要：
We investigate the dependence of the complete system of 22 Lick indices on overall metallicity scaled from solar abundances, [M/H], from the solar value, 0.0, down to the extremely-metal-poor (XMP) value of -6.0, for late-type giant stars (MK luminosity class III, log(g)=2.0) of MK spectral class late-K to late-F (3750 < Teff < 6500 K) of the type that are detected as "fossils" of early galaxy formation in the Galactic halo and in extra-galactic structures. Our investigation is based on synthetic index values, I, derived from atmospheric models and synthetic spectra computed with PHOENIX in LTE and Non-LTE (NLTE), where the synthetic spectra have been convolved to the spectral resolution, R, of both IDS and SDSS (and LAMOST) spectroscopy. We identify nine indices, that we designate "Lick-XMP", that remain both detectable and significantly [M/H]-dependent down to [M/H] values of at least ~-5.0, and down to [M/H] ~ -6.0 in five cases, while also remaining well-behaved . For these nine, we study the dependence of I on NLTE effects, and on spectral resolution. For our LTE I values for spectra of SDSS resolution, we present the fitted polynomial coefficients, C_n, from multi-variate linear regression for I with terms up to third order in the independent variable pairs (Teff, [M/H]), and (V-K, [M/H]), and compare them to the fitted C_n values of Worthey et al. (1994) at IDS spectral resolution.
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