最大的矮星系群星表：瞬态结构还是宇宙的积木？

中文摘要 AI 辅助

elusive 矮星系群为研究最低质量尺度上的层级星系并合提供了难得的机会，但此类关联系统究竟是引力束缚体系还是瞬态结构仍不确定。我们利用暗能量光谱仪巡天（DESI Survey）呈现了最大的孤立矮星系群星表，包含74个系统，每个群拥有三至六个成员。这些群的中值视线速度弥散约为53 km/s，中值穿越时间约为0.37 Gyr。我们发现仅凭恒星质量通常不足以束缚观测到的结构。另一方面，当使用独立推断的恒星-暗物质晕质量关系和NFW势引入暗物质时，在传播观测和暗物质晕模型不确定性后，74个系统中的69个（93%）倾向于束缚解释。对于这69个倾向束缚的系统，动力学摩擦估计表明，如果其成员保留显著的暗物质子晕，在哈勃时间内发生显著的轨道衰减是可能的。我们的结果表明，这些群中的许多是在更庞大后代的组装过程中被捕获的系统，代表了近邻宇宙中持续层级星系增长的最低质量场所之一，也是早期宇宙时代普遍存在的组装模式的可及实验室。

英文摘要

Elusive dwarf galaxy groups provide a rare opportunity to study hierarchical galaxy assembly at the lowest-mass scales, but whether such associations are gravitationally bound systems or transient configurations remains uncertain. We present the largest catalog of isolated dwarf galaxy groups, identified using the DESI Survey, comprising 74 systems with three to six members per group. The groups have a median line-of-sight velocity dispersion of $\sim53$ km s$^{-1}$ and a median crossing time of $\sim0.37$ Gyr. We find that stellar mass alone is generally insufficient to bind the observed configurations. On the other hand, when dark matter is included using independently inferred stellar-to-halo mass relations and NFW potentials, 69 of 74 systems ($93\%$) favor a bound interpretation after propagating observational and halo-model uncertainties. For the 69 bound-favored systems, dynamical-friction estimates indicate that substantial orbital decay within a Hubble time is plausible if their members retain significant dark-matter subhalos. Our results suggest that many of these groups are systems caught during the assembly of more massive descendants, representing some of the lowest-mass sites of ongoing hierarchical galaxy growth in the nearby Universe and accessible laboratories for a mode of assembly expected to have been prevalent at early cosmic epochs.

发表机构

• Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma（俄克拉荷马大学霍默·L·道奇物理与天文系）

机构由 AI 辅助整理，请以论文原文为准。

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6 pages, 3 figures, submitted to ApJ