AI 中文总结
本研究利用COLIBRE流体动力学模拟，探究卫星星系恒星质量-大小关系的起源，发现矮卫星与亮卫星因演化路径不同呈现差异化特征，并揭示了 ram 压力剥离、潮汐作用等过程的影响机制。
AI 中文摘要
我们利用COLIBRE宇宙学流体动力学模拟套件，研究了卫星星系的恒星质量-大小关系。卫星星系偏离了适用于中心星系的关系：在大质量端$\log (M_*/{\rm M}_\odot) > 10.5$，星系大小（定义为三维半质量半径$r_{\rm h,*}$）随质量$r_{\rm h,*} \propto M_*^{0.5}$系统性增大；而在较低质量端$8 < \log(M_*/{\rm M}_\odot) < 10.5$，该关系趋于平缓，星系平均大小几乎与质量无关（$r_{\rm h,*} \approx 3$千秒差距）。在$z=0$处，矮卫星（定义为满足$8 < \log(M_*/{\rm M}_\odot) < 9$的卫星）系统性大于具有相似$M_*$的中心星系。这一趋势在亮卫星（$9 < \log(M_*/{\rm M}_\odot) < 10.5$）中发生反转，亮卫星通常小于质量相近的中心星系。我们将这些趋势归因于卫星落入更大质量宿主暗晕后受到的演化过程影响。落入宿主时，矮卫星通常是富气体、暗物质主导的系统，拥有相对较大的重子诱发核。这些卫星在因冲压压力失去气体后迅速停止恒星形成，中心引力势变浅会引发即时的脉冲式膨胀，随后随着其带核暗物质晕被潮汐作用逐渐剥离，还会发生长期膨胀。相比之下，亮卫星的内部区域由重子主导，能够抵御潮汐作用。中心集中的恒星形成增加了它们的恒星质量，导致其尺寸更小、恒星金属丰度（高出$\approx 0.2$ dex）高于质量相近的中心星系。这些截然不同的卫星演化路径在质量-大小-金属丰度关系中留下了可识别的特征，可与观测结果进行对比。
英文摘要
We study the stellar mass-size relation of satellite galaxies in the COLIBRE suite of cosmological hydrodynamical simulations. Satellites deviate from the relation that holds for centrals galaxies, where at the high mass end, $\log (M_*/{\rm M}_\odot) > 10.5$, sizes (defined as the 3D half-mass radius $r_{\rm h,*}$) increase systematically with mass ($r_{\rm h,*} \propto M_*^{0.5}$), whereas at lower masses, $8 < \log(M_*/{\rm M}_\odot) < 10.5$, the relation flattens and galaxy size becomes, on average, almost independent of mass ($r_{\rm h,*} \approx 3$ kpc). At $z=0$, dwarf satellites (defined as those with $8 < \log(M_*/{\rm M}_\odot) < 9$) are systematically larger than centrals of similar $M_*$. This trend reverses for bright satellites ($9 < \log(M_*/{\rm M}_\odot) < 10.5$), which are typically smaller than centrals of similar mass. We trace these trends to evolutionary processes affecting satellites after infall into the haloes of more massive hosts. At infall, dwarf satellites are typically gas-rich, dark matter-dominated systems with relatively large baryon-induced cores. These satellites quench rapidly after losing their gas to ram pressure, which prompts an immediate impulsive expansion due to the shallowing central potential, followed by secular expansion as their cored dark matter haloes are gradually stripped by tides. In contrast, the inner regions of bright satellites are baryon-dominated and resilient to tides. Centrally concentrated star formation increases their stellar mass, leading to smaller sizes and higher stellar metallicities (by $\approx 0.2$ dex) than those of centrals of similar mass. These distinct satellite evolutionary pathways lead to identifiable features in the mass-size-metallicity relations that may be compared with observations.
Comments12 pages, 8 figures. Submitted to Astronomy & Astrophysics (A&A)
