通过并合形成富含球状星团的超弥散星系
Formation of globular cluster-rich ultra-diffuse galaxies through mergers
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中文总结 AI 辅助
通过高分辨率流体动力学模拟发现，富气体矮星系并合可形成富含球状星团的超弥散星系，且能预测星团质量、旋转与金属丰度弥散的相关趋势。
中文摘要 AI 辅助
我们采用高分辨率、理想化的富气体矮星系并合流体动力学模拟，以测试这类并合是否能形成具有球状星团（GC）系统的超弥散星系（UDG）。我们模拟了1:1和1:2的并合，同时设置了孤立控制模型，并将恒星 overdensities 识别为球状星团候选体（GCCs）。并合残余物演化成弥散支持的类UDG系统，其三维恒星半质量半径$r^{3D}$约为1.9-2.6千秒差距，而孤立矮星系则保持旋转支撑，未形成任何GCCs。潮汐加热和恒星反馈将大部分气体驱逐出暗物质（DM）晕，留下以恒星为主的残余物，其暗物质晕仍呈尖峰状。并合驱动的恒星形成高度成团：在第一次近心点通过后，束缚在大质量星团中的新形成恒星质量占比超过0.5，且此后保持较高水平。到最终快照时，残余物拥有的球状星团数量为：1:1并合形成的残余物有20个，1:2并合形成的残余物有39个，这些球状星团比场星更集中，且与观测到的球状星团数量-暗物质晕质量关系一致。GCCs在质量-大小、速度弥散和密度平面上与观测到的恒星星团匹配。更大质量的星团表现出更强的内部旋转和更宽的金属丰度分布。在其中一个案例中，该并合通过星团内落及后续持续的原位恒星形成产生了一个有核的超弥散星系。这些结果表明，富气体矮星系并合是形成富含球状星团（有时是有核）的超弥散星系的可行途径，并预测了星团质量、旋转和金属丰度-弥散之间的相关趋势，可通过观测进行检验。
英文摘要
We use high-resolution, idealized hydrodynamic simulations of gas-rich dwarf-galaxy mergers to test whether such encounters can form ultra-diffuse galaxies (UDGs) with globular cluster (GC) systems. We simulate 1:1 and 1:2 mergers alongside an isolated control model and identify stellar overdensities as GC candidates (GCCs). The remnants evolve into dispersion-supported, UDG-like systems with three-dimensional stellar half-mass radii $r^{3D} \sim 1.9-2.6$ kpc, while the isolated dwarf remains rotationally supported and forms no GCCs. Tidal heating and stellar feedback expel a large fraction of the gas beyond the dark matter (DM) halo, leaving stellar-dominated remnants whose DM haloes remain cuspy. Merger-driven star formation is highly clustered: the fraction of newly formed stellar mass bound in massive clusters exceeds 0.5 after the first pericentric passage and remains elevated thereafter. By the final snapshot, the remnants host GC populations numbering 20 (1:1) and 39 (1:2), more centrally concentrated than the field stars and consistent with the observed GC number-halo mass relation. The GCCs match observed star clusters in the planes of mass versus size, velocity dispersion, and density. More massive clusters exhibit stronger internal rotation and broader metallicity spreads. In one case, the merger produces a nucleated UDG via cluster inspiral followed by sustained in-situ star formation. These results demonstrate that gas-rich dwarf mergers are a viable pathway to GC-rich (and sometimes nucleated) UDGs, and predict correlated cluster mass, rotation, and metallicity-dispersion trends testable with observations.
