一个用于分离恒星星族年龄的优化H_β指数
An optimized H_βindex for disentangling stellar population ages
摘要：
我们定义了一个新的H_β吸收指数定义H $_{β_o}$，并将其优化为老、中年龄恒星星族的年龄指标。而不是使用恒星光谱，为此目的，我们采用了一个图书馆的恒星星族SED的不同年龄和金属丰度在中等高的光谱分辨率。H $_{β_o}$为我们提供了提高影响标准Hbeta Lick指数定义的年龄-金属度简并性的能力。新的指数，这也已针对光子噪声和速度色散进行了优化，充分的特点与波长漂移，光谱形状，尘埃消光和[α/Fe]丰度比的影响。H_β需要与通常用于测量标准HbetaLick指数定义的光谱相似的光谱。为了说明H $_{β_o}$作为年龄指标的用途和能力，我们将其应用于银河系球状星团和一个精心挑选的样本的早期类型的星系，覆盖范围很广的质量。这里显示的结果对于应用该指数和理解所涉及的不确定性特别有用。
英文摘要：
We have defined a new H_βabsorption index definition, H$_{β_o}$, which has been optimized as an age indicator for old and intermediate age stellar populations. Rather than using stellar spectra, we employed for this purpose a library of stellar population SEDs of different ages and metallicities at moderately high spectral resolution. H$_{β_o}$ provides us with improved abilities for lifting the age-metallicity degeneracy affecting the standard Hbeta Lick index definition. The new index, which has also been optimized against photon noise and velocity dispersion, is fully characterized with wavelength shift, spectrum shape, dust extinction and [alpha/Fe] abundance ratio effects. H_βrequires spectra of similar qualites as those commonly used for measuring the standard Hbeta Lick index definition. Aiming at illustrating the use and capabilities of H$_{β_o}$ as an age indicator we apply it to Milky Way globular clusters and to a well selected sample of early-type galaxies covering a wide range in mass. The results shown here are particularly useful for applying this index and understand the involved uncertainties.
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