论文标题
SDSS-IV漫画：早期星系的[$α$/fe]
SDSS-IV MaNGA: The [$α$/Fe] of Early-Type Galaxies
论文作者
论文摘要
银河系的平均恒星α与铁的丰度比（[$α$/fe]）是银河星形成时间表的指标。重要的是要理解早期型星系（ETG）的恒星形成历史，因为它们的恒星形成过程基本上已经停止。使用Vazdekis等人制造的模型模板，我们应用基于PPXF的光谱拟合方法来估计漫画调查中的196个高信噪比ETG的[$α$/fe]。 1r $ _e $（$σ_{e} $）内的速度分散量从27至270 km/s。我们在1r $ _e^{maj} $椭圆机和log（$σ_{e} $）中找到平均[$α$/fe]之间的平坦关系，即使使用log（$ c $σ_{e} $/km s $ s $ s $ s $^{ - 1}} $> $> 1.9 $ 1.9。但是，在我们排除拟合中的Mg $ _1 $功能之后，这种关系变得积极，这与先前与其他出色的人口模型的结果相符，尽管散布相对较大。它表明，当使用MG $ _b $ index时，与Vazdekis型号的光谱拟合基本上可以给予[$α$/fe]的一致预测，但在使用Mg $ _b $ index时，当他们的$α$ enhanced版本在金属富含金属富含金属富含金属富含金属富含金属富含金属的方案中时，在MG $ _1 $ band上效果不佳。我们建议避免使用该相当广泛的指数，该指数涵盖471Å，因为它可能会遭受其他效果，例如通量校准问题。作为参考，我们还测量了1r $ _e^{maj} $椭圆形内的恒星种群径向梯度。由于旧对象的年龄估计分辨率很低和毫克$ _1 $问题，因此无法忽略这些梯度的不确定性。
The mean stellar alpha-to-iron abundance ratio ([$α$/Fe]) of a galaxy is an indicator of galactic star formation timescale. It is important for understanding the star formation history of early-type galaxies (ETGs) as their star formation processes have basically stopped. Using the model templates which are made by Vazdekis et al., we apply the pPXF based spectral fitting method to estimate the [$α$/Fe] of 196 high signal-to-noise ratio ETGs from the MaNGA survey. The velocity dispersions within 1R$_e$ ($σ_{e}$) range from 27 to 270 km/s. We find a flat relation between the mean [$α$/Fe] within the 1R$_e^{maj}$ ellipses and log($σ_{e}$), even if limiting to the massive sample with log($σ_{e}$/km s$^{-1}$)$>$1.9. However, the relation becomes positive after we exclude the Mg$_1$ feature in our fits, which agrees with the results from the previous work with other stellar population models, albeit with relatively large scatter. It indicates that the spectral fits with Vazdekis models could give basically the consistent predictions of [$α$/Fe] with previous studies when the Mg$_b$ index is used, but do not work well at the Mg$_1$ band when their $α$-enhanced version is employed in the metal-rich regime. We suggest avoiding this rather wide index, which covers 471Å, as it might suffer from other effects such as flux-calibration issues. For reference, we also measure the stellar population radial gradients within 1R$_e^{maj}$ ellipses. Due to the low resolution of age estimations for old objects and the Mg$_1$ issue, the uncertainties of these gradients cannot be neglected.
