SDSS-IV MaNGA: Stellar M/L gradients and the M/L-colour relation in galaxies
SDSS-IV MaNGA: Stellar M/L gradients and the M/L-colour relation in galaxies
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SDSS-IV MaNGA：恒星 M/L 梯度和星系中的 M/L 颜色关系
DOI：
10.1093/mnras/stab2341
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发表时间：
2021
影响因子：
4.8
通讯作者：
Yan Renbin
中科院分区：
文献类型：
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作者：
Ge Junqiang;Mao Shude;Lu Youjun;Cappellari Michele;Long Richard J.;Yan Renbin
星系在SDSSr波段的质量光比梯度（M*/Lr）取决于其质量组装历史，这是在其形态和年龄，金属丰度和恒星初始质量函数（IMF）的梯度印记。以SDSS DR 15中公布的2051个恒星质量从109到1012 M_r的星系为样本，我们专注于没有合并和棒特征的面对面星系，并研究了2D M_r（M*/Lr）对其他星系性质的依赖性，包括假设固定的Salpeter IMF作为质量归一化参考的M */Lr-颜色关系。大质量星系的中位梯度为M*/Lr <$−0.1（即中心处的M */Lr较大），在M *<$1010 M <$附近变得平坦，在最低质量处变为M*/Lr <$0.1。半光半径内的M */LR随着星系恒星质量的增加而增加;在每个质量仓中，早型星系具有最高值，而纯盘晚型星系具有最小值。相关分析表明，质量加权恒星年龄是影响M */Lr剖面的主要参数，因为当半光半径内的比星星形成率（sSFR）大于10− 3 Gyr −1时，光度加权年龄很容易受到星星形成的影响。随着sSFR梯度的增加，可以获得更陡的负斜率（M*/Lr）。随着sSFR的增加，M */L色关系的斜率的分散性增加，例如，在M */L versusg − r图中，星暴后星系的斜率可以从整体值0.87平坦化到0.45。因此，将星系颜色转换为M */L应该小心，特别是对于那些具有年轻光度加权恒星年龄的星系，它们可能具有完全不同的星星形成历史。
The stellar mass-to-light ratio gradient in SDSSr-band ∇(M*/Lr) of a galaxy depends on its mass assembly history, which is imprinted in its morphology and gradients of age, metallicity, and stellar initial mass function (IMF). Taking a MaNGA sample of 2051 galaxies with stellar masses ranging from 109to 1012M⊙released in SDSS DR15, we focus on face-on galaxies, without merger and bar signatures, and investigate the dependence of the 2D ∇(M*/Lr) on other galaxy properties, includingM*/Lr-colour relationships by assuming a fixed Salpeter IMF as the mass normalization reference. The median gradient is ∇M*/Lr∼ −0.1 (i.e. theM*/Lris larger at the centre) for massive galaxies, becomes flat aroundM*∼ 1010M⊙and change sign to ∇M*/Lr∼ 0.1 at the lowest masses. TheM*/Lrinside a half-light radius increases with increasing galaxy stellar mass; in each mass bin, early-type galaxies have the highest value, while pure-disc late-type galaxies have the smallest. Correlation analyses suggest that the mass-weighted stellar age is the dominant parameter influencing theM*/Lrprofile, since a luminosity-weighted age is easily affected by star formation when the specific star formation rate (sSFR) inside the half-light radius is higher than 10−3Gyr−1. With increased sSFR gradient, one can obtain a steeper negative ∇(M*/Lr). The scatter in the slopes ofM*/L-colour relations increases with increasing sSFR, for example, the slope for post-starburst galaxies can be flattened to 0.45 from the global value 0.87 in theM*/Lversusg−rdiagram. Hence converting galaxy colours toM*/Lshould be done carefully, especially for those galaxies with young luminosity-weighted stellar ages, which can have quite different star formation histories.