论文标题
快速生活，死亡$α$ - 增强：银河系中断的矮人星系的质量金属性 - $α$
Live Fast, Die $α$-Enhanced: The Mass-Metallicity-$α$ Relation of the Milky Way's Disrupted Dwarf Galaxies
论文作者
论文摘要
银河系的卫星星系（“幸存的矮人”）已被研究数十年来是低质量政权化学进化的独特探针。在这里，我们将此类研究扩展到“破坏的矮人”，其碎片构成了恒星的光环。 We present abundances ([Fe/H], [$α$/Fe]) and stellar masses for nine disrupted dwarfs with $M_{\star}\approx10^{6}-10^{9}M_{\odot}$ from the H3 Survey (Sagittarius, $Gaia$-Sausage-Enceladus, Helmi Streams, Sequoia, Wukong/LMS-1，Cetus，Thamnos，I'itoi，Orphan/Chenab）。幸存的和破坏的矮人在化学上是不同的：在固定质量下，破坏的矮人是系统的金属贫困和$α$增强的。矮人的干扰定义了质量金属关系（MZR），其斜率与$ z = 0 $ MZR相似，其次是幸存的矮人，但将金属的金属降低$δ$ [fe/h h] $ \ y $ \ tem \ fe/h h] $ \ yout.3-3-0.4 $ dex。从$ z = 0 $ mzr的较大偏移量较大的矮人更具$α$增强。在模拟和观察中，在更高的红移下形成的具有较高$δ$ [fe/h]的星系 - 利用这一点，我们推断出的矮矮人具有典型的星形形成截断，$ z _ {\ rm {trunc}}} {\ sim} {\ sim} {\ sim} {\ sim} 1-2 $。我们将化学推断的$ z _ {\ rm {trunc}} $与动态推断的积聚红移进行了比较，并且仅在积聚后才能找到几乎所有矮人。破坏和幸存的矮人之间的差异可能是因为被破坏的矮人在较高的红移和在靠近银河系附近的较密集的暗物质中迅速组装了质量。我们的结果对低质量星系的新考古限制放置在无法访问的高$ $ z $研究上：（i）MZR沿并行轨道的红移演变，但偏移到较低的金属性延伸至$ m _ {\ star} \ star} \ loct10^{6} {6} {6} -10} -10} -10} -10} {9} {9} M _} （ii）$ z \ of2-3 $的星系是$α$增强的，[$α$/fe] $ \ oft0.4 $。
The Milky Way's satellite galaxies ("surviving dwarfs") have been studied for decades as unique probes of chemical evolution in the low-mass regime. Here we extend such studies to the "disrupted dwarfs", whose debris constitutes the stellar halo. We present abundances ([Fe/H], [$α$/Fe]) and stellar masses for nine disrupted dwarfs with $M_{\star}\approx10^{6}-10^{9}M_{\odot}$ from the H3 Survey (Sagittarius, $Gaia$-Sausage-Enceladus, Helmi Streams, Sequoia, Wukong/LMS-1, Cetus, Thamnos, I'itoi, Orphan/Chenab). The surviving and disrupted dwarfs are chemically distinct: at fixed mass, the disrupted dwarfs are systematically metal-poor and $α$-enhanced. The disrupted dwarfs define a mass-metallicity relation (MZR) with a similar slope as the $z=0$ MZR followed by the surviving dwarfs, but offset to lower metallicities by $Δ$[Fe/H]$\approx0.3-0.4$ dex. Dwarfs with larger offsets from the $z=0$ MZR are more $α$-enhanced. In simulations as well as observations, galaxies with higher $Δ$[Fe/H] formed at higher redshifts -- exploiting this, we infer the disrupted dwarfs have typical star-formation truncation redshifts of $z_{\rm{trunc}}{\sim}1-2$. We compare the chemically inferred $z_{\rm{trunc}}$ with dynamically inferred accretion redshifts and find almost all dwarfs are quenched only after accretion. The differences between disrupted and surviving dwarfs are likely because the disrupted dwarfs assembled their mass rapidly, at higher redshifts, and within denser dark matter halos that formed closer to the Galaxy. Our results place novel archaeological constraints on low-mass galaxies inaccessible to direct high-$z$ studies: (i) the redshift evolution of the MZR along parallel tracks but offset to lower metallicities extends to $M_{\star}\approx10^{6}-10^{9}M_{\odot}$; (ii) galaxies at $z\approx2-3$ are $α$-enhanced with [$α$/Fe]$\approx0.4$.
