发表机构
Chinese Academy of Sciences; Shanghai Astronomical Observatory, Chinese Academy of Sciences; University of Chinese Academy of Sciences; Indian Institute of Astrophysics (IIA); Fudan University; Peking University; Kavli Institute for Astronomy and Astrophysics, Peking University; Department of Physics, Fudan University; Department of Astronomy, School of Physics, Peking University; International Centre for Radio Astronomy Research, University of Western Australia; University of Western Australia（中国科学院; 中国科学院上海天文台; 中国科学院大学; 印度天体物理研究所; 复旦大学; 北京大学; 北京大学科维理天文与天体物理研究所; 复旦大学物理系; 北京大学物理学院天文学系; 西澳大利亚大学国际无线电天文研究中心; 西澳大利亚大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究人员利用DESI光谱对约3万个星系开展观测，发现恒星形成星系以流出为主、宁静星系存在流入，揭示了星系中广泛的气体吸积与循环规律，建立了气体流动与星系演化的观测关联框架。
AI 中文摘要
维持恒星形成所需的冷气体流入在模拟中是基础，但在观测上却难以捉摸。利用暗能量光谱仪（DESI）对约30000个星系的光谱观测，我们在20%至50%的样本中识别出了速度约为100 km/s的相干流入气体，实现了星系际气体流的总体普查。我们发现了一个显著的反转：宁静星系中存在流入，而恒星形成系统则以引力束缚的流出为主。在固定年龄下，具有流入、流出或无/弱流动的星系拥有相似的质量、环境和结构，表明这些属性并不能区分流动状态。相反，气体流动状态与恒星族群年龄和近期演化历史相关，符合两种机制中与年龄相关的气体流动规律。在一些恒星形成星系中，升高的恒星形成面密度驱动的流出会以约0.5 Gyr的时间尺度循环，符合星系喷泉模型。在宁静系统中，低水平的“滴落式”流入持续存在，符合缓慢冷却的富集晕气体和弱射电模式核活动。宽气体相金属丰度分布——且未出现原始稀释特征——表明检测到的流入主要是循环或富集的。可检测性受尘埃、电离和几何结构的调制：在恒星形成星系盘中，流入气体位于盘平面附近，被遮蔽或电离，而流出宿主则表现出更高的尘埃和金属含量。随着恒星形成活动减弱，冷流出信号减弱，循环或缓慢冷却的气体更易被检测为流入。后星暴星系为这一转变提供了快照。我们的结果解决了观测流入稀缺的问题，为当前星系中广泛的气体吸积和循环提供了证据，并建立了将气体流动与恒星形成、化学演化及星系结构关联的观测框架。
英文摘要
Cool-gas inflows, required to sustain star formation, have been fundamental in simulations yet remained observationally elusive. Using DESI spectroscopy of ~30,000 galaxies, we identify coherent inflowing gas (~100 km/s) in 20-50% of the sample, yielding a population-level census of gas flows. We uncover a striking inversion: inflows are detected in quiescent galaxies, whereas star-forming systems are dominated by gravitationally bound outflows. At fixed age, galaxies with inflows, outflows, or no/weak flows share similar masses, environments, and structures, indicating that these properties do not differentiate flow states. Instead, gas-flow state is linked to stellar population age and recent evolutionary history, consistent with age-dependent gas flows in two regimes. In some star-forming galaxies, elevated star formation surface densities drive outflows that recycle on ~0.5 Gyr timescales, consistent with a galactic fountain. In quiescent systems, low-level ``drizzling'' inflows persist, consistent with slowly cooling enriched halo gas and weak radio-mode nuclear activity. Broad gas-phase metallicity distributions---and absence of a pristine dilution signature---indicate that detected inflows are predominantly recycled or enriched. Detectability is modulated by dust, ionization, and geometry: in star-forming disks, inflowing gas lies near the disk plane and is obscured or ionized, while outflow hosts exhibit higher dust and metal content. As star formation declines, cold-outflow signatures weaken, and recycled or slowly cooling gas is more readily detected as inflow. Post-starburst galaxies provide snapshots of this transition. Our results resolve the scarcity of observed inflows, provide evidence for widespread gas accretion and recycling in present day galaxies, and establish an observational framework linking gas flows to star formation, chemical evolution, and galaxy structure.
Comments73 pages, 25 Figures (5 Main + 8 Extended Data + 12 Supplementary), submitted on 6th March 2026
