标题： SAMI-Fornax矮星系巡天III：从星团到本星系群的矮星系中[$α$/Fe]的演化 显示英文标题

标题： The SAMI-Fornax Dwarfs Survey III: Evolution of [$α$/Fe] in dwarfs, from Galaxy Clusters to the Local Group

摘要： 利用来自SAMI积分视场光谱仪的非常深且具有高光谱分辨率的数据，我们研究了弗纳克星系团中矮星系的恒星群体性质，最低达到$10^{7}$ M$_{\odot}$的恒星质量，这一研究在本星系群之外尚属首次。 我们通过全谱拟合来获取恒星群体参数。 加入来自重新分析的ATLAS$^{3D}$项目的巨椭圆星系以及银河系的卫星星系，我们得到了一个覆盖$10^{4}$至$10^{12} M_{\odot}$恒星质量范围的星系样本。 利用这个大范围的质量区间，我们发现质量-金属丰度关系并非线性。 我们还发现，整个样本的 [$\alpha$/Fe]-恒星质量关系呈现出U形，在 [$\alpha$/Fe] 处有最小值，对应于质量在 [$10^{9}-10^{10} M_{\odot}$] 之间的星系。 [$\alpha$/Fe] 和恒星质量之间的关系可以这样理解： 当最暗弱的星系进入星团环境时，会触发一次快速的恒星形成爆发，随后气体成分会被各种淬灭机制吹散。 这种快速的恒星形成会导致较高的 [$\alpha$/Fe] 值，类似于银河系晕的情况。 质量更大的星系能够更长时间地保留其气体，并经历多次恒星形成爆发，因此具有较低的 [$\alpha$/Fe] 值。 对于质量较大的星系，恒星群体受到内部过程的调控，导致 [$\alpha$/Fe] 随质量增加而升高。 我们通过展示 [$\alpha$/Fe] 与三个附近星团以及银河系晕的距离相关联来验证这一模型。 显示英文摘要

摘要： Using very deep, high spectral resolution data from the SAMI Integral Field Spectrograph we study the stellar population properties of a sample of dwarf galaxies in the Fornax Cluster, down to a stellar mass of $10^{7}$ M$_{\odot}$, which has never been done outside the Local Group. We use full spectral fitting to obtain stellar population parameters. Adding massive galaxies from the ATLAS$^{3D}$ project, which we re-analysed, and the satellite galaxies of the Milky Way, we obtained a galaxy sample that covers the stellar mass range $10^{4}$ to $10^{12} M_{\odot}$. Using this large range we find that the mass - metallicity relation is not linear. We also find that the [$\alpha$/Fe]-stellar mass relation of the full sample shows a U-shape, with a minimum in [$\alpha$/Fe] for masses between $10^{9}-10^{10} M_{\odot}$. The relation between [$\alpha$/Fe] and stellar mass can be understood in the following way: When the faintest galaxies enter the cluster environment, a rapid burst of star formation is induced, after which the gas content is blown away by various quenching mechanisms. This fast star formation causes high [$\alpha$/Fe] values, like in the Galactic halo. More massive galaxies will manage to keep their gas longer and form several bursts of star formation, with lower [$\alpha$/Fe] as a result. For massive galaxies, stellar populations are regulated by internal processes, leading to [$\alpha$/Fe] increasing with mass. We confirm this model by showing that [$\alpha$/Fe] correlates with clustercentric distance in three nearby clusters, and also in the halo of the Milky Way.