发表机构
Instituto Nacional de Pesquisas Espaciais; Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas; Kavli Institute for Cosmological Physics, University of Chicago; Department of Astronomy & Astrophysics, University of Chicago; Observatório Nacional, MCTI（国家空间研究所; 圣保罗大学天文、地球物理和大气科学研究所; 芝加哥大学卡弗里宇宙物理学研究所; 芝加哥大学天文学与天体物理学系; 国家天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究结合盖亚天体测量与光谱数据，识别出107个Typhon恒星流候选成员，其金属丰度弥散度支持矮星系起源，并揭示其高偏心率轨道特征，表明其为近期被瓦解的矮星系残骸。
AI 中文摘要
在星系形成的层级模型中，银河系的恒星晕通过矮星系的连续吸积而组装形成。虽然许多由此产生的子结构已被识别，但最近发现的Typhon恒星流的起源仍不明确，因为仅凭动力学数据不足以区分球状星团和矮星系前身。为解决这一问题，我们将盖亚（Gaia）的天体测量数据与现有巡天的光谱数据相结合，全面分析该恒星流的化学和动力学性质。我们识别出107个候选成员，显著扩大了已知样本。其中三个候选者位于55千秒差距（kpc）之外，最远者距离达67 kpc，进一步支持了Typhon推断的较大远心点距离。我们的分析得出平均金属丰度为[Fe/H]=-1.42±0.07，金属丰度弥散度为σ_[Fe/H]=0.26^{+0.06}_{-0.05} dex。这一金属丰度弥散度支持Typhon恒星流起源于矮星系。Typhon的高轨道能量与其近期吸积一个完全瓦解的矮星系（恒星质量范围在10^6 M_⊙ < M_* ≲ 10^7 M_⊙）相一致。此外，Typhon是银河系晕中唯一表现出如此极端轨道偏心率（e ≳ 0.85）的主要矮星系恒星流。我们推测，来自高偏心率并合的矮星系恒星流比那些在圆轨道上的恒星流更快地完全消散，这与Typhon提出的近期吸积一致。额外的处于高偏心率轨道上的矮星系恒星流应可通过下一代光度巡天以及盖亚太空任务的未来数据发布来发现。
英文摘要
In the hierarchical model of galaxy formation, the Milky Way's stellar halo assembles through the successive accretion of dwarf galaxies. While many resulting substructures have been identified, the origin of the recently discovered Typhon stellar stream remains ambiguous, as dynamical data alone are insufficient to distinguish between a globular cluster and a dwarf galaxy progenitor. To resolve this, we combine astrometry from Gaia with spectroscopic data from available surveys to comprehensively analyze the stream's chemical and dynamical properties. We identify 107 candidate members, significantly expanding the known sample. Three of these candidates lie beyond $55\,\mathrm{kpc}$, with the farthest at $67\,\mathrm{kpc}$, lending further support to Typhon's inferred large apocentric distance. Our analysis yields a mean metallicity of $\rm[Fe/H]=-1.42\pm0.07$ and a metallicity dispersion of $σ_{\text{[Fe/H]}} = 0.26^{+0.06}_{-0.05}$ dex. This metallicity dispersion supports a dwarf-galaxy origin for the Typhon stream. Typhon's high orbital energy is consistent with a relatively recent accretion of a fully disrupted dwarf galaxy with a stellar mass in the range of $10^6 M_{\odot} < M_\star \lesssim 10^7 M_{\odot}$. Furthermore, Typhon is the only major dwarf-galaxy stellar stream in the Milky Way's halo to exhibit such an extreme orbital eccentricity of $e \gtrsim 0.85$. We conjecture that dwarf-galaxy streams from high-eccentricity mergers are fully dissolved much more rapidly than those on circular orbits, in line with Typhon's proposed recent accretion. Additional dwarf-galaxy stellar streams on high-eccentricity orbits should be discoverable with next-generation photometric surveys as well as future releases from the Gaia space mission.
CommentsSubmitted to ApJ
