论文标题
Sagittarius恒星流的相位属性和化学源至极度金属贫困（$ \ rm [fe/h] \ Lessim -3 $）制度
Phase-space Properties and Chemistry of the Sagittarius Stellar Stream Down to the Extremely Metal-poor ($\rm[Fe/H] \lesssim -3$) Regime
论文作者
论文摘要
在这项工作中，我们研究了射手座（SGR）流的相空间和化学特性，这是由于持续破坏Sgr Dwarf球形（DSPH）Galaxy所产生的潮汐尾巴，重点介绍其非常金属贫困（VMP; $ \ rm [Fe/H] <-2 $）的内容。我们分别将SEGUE的光谱和天体信息和$ GAIA $ EDR3与来自新的$ \ texttt {starhorse} $ Spectro-Photopermeptric代码的新大规模运行中的数据产品结合在一起。我们的选择标准产生$ {\ sim} 1600 $流成员，包括$ {>} 200 $ VMP星星。我们发现SGR流的领先臂（$ b> 0^\ circ $）比落后一（$ b <0^\ circ $）比$ {\ sim} 0.2 $ dex更具金属贫困。有了一个转弯和次级恒星的子样本，我们估计该子结构的恒星种群比厚磁盘年龄较大。借助SGR系统的$ n $体型模型，我们验证了较早剥离的模拟粒子（$ {>} 2 $ gyr ogo）具有与低金属流星星相似的当今相位空间属性。相反，最近被剥离的人（$ {<} 2 $ gyr）优先类似于富含金属的（$ \ rm [fe/h]> -1 $）。运动学与化学之间的这种相关性可以通过在SGR DSPH中的动态热，中心浓度较低且较高的金属贫困群体的存在来解释，这意味着该星系能够在其提取前发展金属性梯度。最后，我们在SGR流中发现了几个具有碳增强的金属罚款（$ \ rm [c/fe]> +0.7 $和$ \ rm [fe/h] \ rm [fe/h] \ leq -1.5 $）的星星，这与当前无法在此类对象的地方观察到其剩余核心的当前观察到。
In this work, we study the phase-space and chemical properties of Sagittarius (Sgr) stream, the tidal tails produced by the ongoing destruction of Sgr dwarf spheroidal (dSph) galaxy, focusing on its very metal-poor (VMP; $\rm[Fe/H] < -2$) content. We combine spectroscopic and astrometric information from SEGUE and $Gaia$ EDR3, respectively, with data products from a new large-scale run of $\texttt{StarHorse}$ spectro-photometric code. Our selection criteria yields ${\sim}1600$ stream members, including ${>}200$ VMP stars. We find the leading arm ($b>0^\circ$) of Sgr stream to be more metal-poor, by ${\sim}0.2$ dex, than the trailing one ($b<0^\circ$). With a subsample of turnoff and subgiant stars, we estimate this substructure's stellar population to be ${\sim}1$ Gyr older than the thick disk's. With the aid of an $N$-body model of the Sgr system, we verify that simulated particles stripped earlier (${>}2$ Gyr ago) have present-day phase-space properties similar to lower-metallicity stream stars. Conversely, those stripped more recently (${<}2$ Gyr) are preferentially more akin to metal-rich ($\rm[Fe/H] > -1$) members of the stream. Such correlation between kinematics and chemistry can be explained by the existence of a dynamically hotter, less centrally-concentrated, and more metal-poor population in Sgr dSph prior to its disruption, implying that this galaxy was able to develop a metallicity gradient before its accretion. Finally, we discovered several carbon-enhanced metal-poor ($\rm[C/Fe] > +0.7$ and $\rm[Fe/H] \leq -1.5$) stars in Sgr stream, which is in tension with current observations of its remaining core where such objects are not found.
