星系际介质耗竭驱动IllustrisTNG中的卫星星系熄灭
Circumgalactic medium depletion drives satellite quenching in IllustrisTNG
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中文总结 AI 辅助
本研究利用IllustrisTNG模拟星系，发现热星系际介质（CGM）的逐渐耗竭是卫星星系恒星形成缓慢终止的关键，卫星星系并合后约4.2亿年损失90%热CGM，熄灭模式符合延迟后快速熄灭情景。
中文摘要 AI 辅助
卫星星系主导了低恒星质量（$M_\blackstar \backsimeq 10^{10}~\rm M_\blackodot$）下的熄灭星系群体，但识别哪些过程会终止它们的恒星形成、这些过程的相对重要性以及发生的时标，仍是星系演化领域的核心问题。我们利用IllustrisTNG中类MaNGA的模拟星系来剖析不同的卫星星系熄灭路径，特别关注熄灭阶段星系际介质（CGM）的作用。我们重建了约7300个星系（其中2800个为卫星星系）的重子、暗物质、结构和化学演化历史，以并合后的时间作为熄灭过程展开的物理轴。卫星星系在整个熄灭过程中保持旋转支撑的恒星运动学，仅在恒星质量$M_\blackstar \backsimeq 10^{10.5}~\rm M_\blackodot$的系统中出现受扰动的速度场。我们首次呈现了并合后热气体和冷气体储层耗竭的耦合时间演化：卫星星系在约$4.2^{+0.6}_{-0.6}$ Gyr内损失了约90%的热CGM，该比例随驻留时间增加而变化，且与恒星质量无关。热气体质量与恒星形成率（SFR）呈强相关，这确立了CGM作为长期燃料储层的地位，与熄灭的中心星系不同，中心星系保留着可能由活动星系核（AGN）反馈维持的大质量热晕。现今的熄灭卫星星系比恒星形成星系更早被并合（分别为6.5$^{+0.3}_{-0.3}$ Gyr前和4.3$^{+0.3}_{-0.3}$ Gyr前），在并合后至少形成约3 Gyr的恒星，之后才急剧下降，这与延迟后快速熄灭的情景一致。卫星星系几乎不损失恒星质量，但它们的气体被耗尽，且暗物质和贫金属的恒星外围被潮汐剥离，在固定质量下，卫星星系比中心星系更致密、金属丰度更高。我们的结果表明，热CGM的逐渐侵蚀是连接并合与恒星形成缓慢终止的关键环节。
英文摘要
Satellite galaxies dominate the quenched population at low stellar masses ($M_\star \lesssim 10^{10}~\rm M_\odot$), yet identifying which processes shut down their star formation, their relative importance, and on what timescales, remains a central problem in galaxy evolution. We use MaNGA-like mock galaxies from IllustrisTNG to dissect different satellite quenching pathways, paying special attention to the role of the circumgalactic medium (CGM) during quenching phase. We reconstruct the baryonic, dark matter, structural, and chemical histories of $\sim$7 300 galaxies (2 800 satellites), using time since infall as the physical axis along which quenching unfolds. Satellites retain rotation-supported stellar kinematics throughout quenching, with disturbed velocity fields confined to systems with $M_\star \lesssim 10^{10.5}~\rm M_\odot$. For the first time, we present the coupled time evolution of the depletion of both the hot and cool gas reservoirs after infall: satellites lose $\sim$90% of their hot CGM within $\sim$$4.2^{+0.6}_{-0.6}$ Gyr, increasing with residence time and independent of stellar mass. The hot gas mass correlates strongly with SFR, establishing the CGM as the long-term fuel reservoir, unlike quenched centrals, which retain massive hot halos likely maintained by AGN feedback. Present-day quenched satellites were accreted earlier than star-forming ones (6.5$^{+0.3}_{-0.3}$ vs. 4.3$^{+0.3}_{-0.3}$ Gyr ago), forming stars for at least $\sim$3 Gyr after infall before declining sharply, consistent with a delayed-then-rapid quenching scenario. Losing little stellar mass, yet with their gas depleted and their dark matter and metal-poor stellar outskirts tidally stripped, satellites emerge more compact and metal-rich than centrals at fixed mass. Our results suggest the gradual erosion of the hot CGM as the key link connecting infall to the slow shutdown of star formation.
