利用中分辨率（$R\sim11,000$）麦哲伦/IMACS光谱对天鹤座I超暗矮星系（UFD）进行了化学动力学研究。我们确定了八个确认成员的鹤座我，根据其低金属丰度和相干径向速度，和四个候选成员，只有速度的推导。与以前的工作相比，我们发现天鹤座I具有非常低的平均金属丰度$\langle$ [Fe/H] $\rangle = -2.62 \pm 0.11$ dex，使其成为最贫金属的UFD之一。天鹤座I的系统径向速度为$-143.5\pm1.2$ km s $^{-1}$，速度色散为$σ_{\text{rv}} = 2.5^{+1.3}_{-0.8}$ km s $^{-1}$，这导致动力学质量为$M_{1/2} (r_h) = 8^{+12}_{-4} \times 10^5$ M $_{\odot}$，质光比为M/L $_V$ = $440^{+650}_{-250}$ M $_\odot$ /L $_\odot$。在动力学平衡的假设下，我们的分析证实了天鹤座I是一个暗物质主导的UFD（M/L $> 80$ M $_\odot$ /L $_\odot$）。然而，我们不解决金属分散（$σ_{\text{[Fe/H]}} < 0.44$ dex）。我们的研究结果表明，天鹤座I是一个相当典型的UFD的参数，同意质量金属丰度和金属丰度光度的趋势，微弱的星系。这一一致性表明，天鹤座I并没有因为与银河系的潮汐相遇而失去特别显著的质量，这与它的轨道参数一致。有趣的是，在未知是否会扰乱潮汐的UFD中，鹤一号的中心密度（$ρ_{1/2} \sim 3.5_{-2.1}^{+5.7} \times 10^7$ M $_\odot$ kpc $^{-3}$）是最低的。UFD形成和演化的模型需要解释这些中心密度的多样性，以及这些遗迹星系外部区域的多样性。
英文摘要：
We present a chemodynamical study of the Grus I ultra-faint dwarf galaxy (UFD) from medium-resolution ($R\sim11,000$) Magellan/IMACS spectra of its individual member stars. We identify eight confirmed members of Grus I, based on their low metallicities and coherent radial velocities, and four candidate members for which only velocities are derived. In contrast to previous work, we find that Grus I has a very low mean metallicity of $\langle$[Fe/H]$\rangle = -2.62 \pm 0.11$ dex, making it one of the most metal-poor UFDs. Grus I has a systemic radial velocity of $-143.5\pm1.2$ km s$^{-1}$ and a velocity dispersion of $σ_{\text{rv}} = 2.5^{+1.3}_{-0.8}$ km s$^{-1}$ which results in a dynamical mass of $M_{1/2} (r_h) = 8^{+12}_{-4} \times 10^5$ M$_{\odot}$ and a mass-to-light ratio of M/L$_V$ = $440^{+650}_{-250}$ M$_\odot$/L$_\odot$. Under the assumption of dynamical equilibrium, our analysis confirms that Grus I is a dark-matter-dominated UFD (M/L $> 80$ M$_\odot$/L$_\odot$). However, we do not resolve a metallicity dispersion ($σ_{\text{[Fe/H]}} < 0.44$ dex). Our results indicate that Grus I is a fairly typical UFD with parameters that agree with mass-metallicity and metallicity-luminosity trends for faint galaxies. This agreement suggests that Grus I has not lost an especially significant amount of mass from tidal encounters with the Milky Way, in line with its orbital parameters. Intriguingly, Grus I has among the lowest central density ($ρ_{1/2} \sim 3.5_{-2.1}^{+5.7} \times 10^7$ M$_\odot$ kpc$^{-3}$) of the UFDs that are not known to be tidally disrupting. Models of the formation and evolution of UFDs will need to explain the diversity of these central densities, in addition to any diversity in the outer regions of these relic galaxies.
我们目前的结果，从光谱观测与密歇根/麦哲伦光纤系统（M2 FS）的$147$恒星目标的视线沿线的新发现的“ultrafeak”恒星系统杜鹃2（Tuc 2）和鹤1（Gru 1）。同时估计的视线速度和恒星大气参数的基础上，我们确定8和7星Tuc 2和Gru 1，分别可能的成员。我们的Tuc 2样本足以解决$8.6_{-2.7}^{+4.4}$ km s $^{-1}$关于平均$-129.1_{-3.5}^{+3.5}$ km s $^{-1}$（太阳静止框架）的内部速度色散，并估计平均金属丰度[Fe/H]= $-2.23_{-0.12}^{+0.18}$。这些结果Tuc 2的化学动力学标度关系其次是矮星系，这表明一个占主导地位的暗物质成分与动力学质量$2.7_{-1.3}^{+3.1}\times 10^6$ $\mathrm{M}_{\odot}$封闭在中央$\sim 160$ PC，和动力学质量-光比$1900_{-900}^{+2200}$ $\mathrm{M}_{\odot}/L_{V,\odot}$。对于Gru 1，我们估计平均速度为$-140.5_{-1.6}^{+2.4}$ km s $^{-1}$，平均金属丰度为[Fe/H]= $-1.42_{-0.42}^{+0.55}$，但我们的样本没有解决Gru 1的速度色散。Tuc 2和Gru 1在银河系相空间中的径向坐标表明…
Deep Imaging of Grus II and Horologium II: Structure and Extent of Two Ultra-Faint Milky Way Satellites
University of Arizona（亚利桑那大学）；Stanford University（斯坦福大学）；Dartmouth College（达特茅斯学院）；Rubin Observatory/AURA（鲁宾天文台/美国大学天文研究协会）；University of Chicago（芝加哥大学）
Multi-Object Spectroscopy of Galaxy Clusters at $z \sim 0.95$ in Ultra Deep Survey Field with Different Star-formation Properties and Large-scale Environments
A Chemodynamical Census of the Milky Way's Ultra-Faint Compact Satellites. I. A First Population-Level Look at the Internal Kinematics and Metallicities of 19 Extremely-Low-Mass Halo Stellar Systems
Yale University（耶鲁大学）；University of Toronto（多伦多大学）；Dunlap Institute for Astronomy & Astrophysics（邓普勒天文学与天体物理学研究所）；University of Virginia（弗吉尼亚大学）；Carnegie Institution for Science（卡内基科学机构）；University of Chicago（芝加哥大学）；Kavli Institute for Cosmological Physics（卡弗里宇宙物理学研究所）；Fermi National Accelerator Laboratory（费米国家加速器实验室）
Spectroscopic Confirmation of the Milky Way Satellites Boötes V and Leo Minor I and the LMC Satellite DELVE 2: Three Small Ultra-Faint Dwarf Galaxies
Yale University（耶鲁大学）；Carnegie Institution for Science（卡内基科学研究所）；University of Toronto（多伦多大学）；University of Virginia（弗吉尼亚大学）；Space Telescope Science Institute（太空望远镜科学研究所）；Johns Hopkins University（约翰斯·霍普金斯大学）；University of Chicago（芝加哥大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）
通过多目标光谱观测，证认 Boötes V、Leo Minor I 和 DELVE 2 为超暗弱矮星系，并首次确认 DELVE 2 为 LMC 的长期束缚卫星，提出基于半光半径和表面亮度的分类判据。
