发表机构
University of Victoria; University College London; Universidade Federal do Rio Grande; Max-Planck-Institut für Radioastronomie; University of Edinburgh; Peking University（维多利亚大学; 伦敦大学学院; 南里奥格兰德联邦大学; 马克斯·普朗克射电天文研究所; 爱丁堡大学; 北京大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用MUMMI-DECaLS星表与ALFALFA巡天交叉匹配，通过21厘米谱堆叠发现并合后星系的HI气体演化强烈依赖于并合后时间及恒星形成状态，恒星形成型星系呈现先过剩后亏损再恢复的模式，而熄灭型星系持续HI亏损但仍有大量残余气体。
AI 中文摘要
（删节版）在本工作中，我们研究了原子氢（HI）气体在星系并合生命周期中的作用。为了识别处于并合中的星系并预测其并合后经过的时间，我们提出了多模型并合识别器（MUMMI）机器学习视觉流水线的一个扩展，并将其应用于暗能量相机遗留巡天（DECaLS）成像数据。新的MUMMI-DECaLS星表包含19,951个并合后星系，其中14,638个具有稳健的并合后时间（T_PM）预测。我们将MUMMI-DECaLS并合后星系星表与阿雷西博遗产快速ALFA（ALFALFA）巡天进行交叉匹配。对于由此识别出的752个并合后星系以及一个匹配的对照样本，我们生成了21厘米发射的中值谱堆叠，发现并合后星系相比非相互作用星系HI亏损0.11 dex。当按T_PM分箱时，我们发现HI亏损（或过剩）强烈依赖于并合后经过的时间以及星系是恒星形成型还是熄灭型。特别是恒星形成型并合后星系表现出随T_PM的强烈HI演化，在并合后立即出现0.1 dex的MHI过剩，在0.16 < T_PM < 0.96 Gyr时出现0.3 dex的MHI亏损，并在并合后约1.5 Gyr时恢复正常气体质量。另一方面，尽管在恒星形成率、恒星质量和红移上进行了匹配，熄灭型并合后星系在并合后短期和长期时间内均表现为HI亏损。然而，即使在这些晚期熄灭型并合后星系中，仍保留了大量的HI（>10^9 M_sun），这代表了未来可能重新点燃恒星形成的资源。我们的结果展示了量化并合中HI行为的复杂性，这不仅取决于时间，还取决于恒星形成状态，这可能会使不同研究和样本之间的比较变得复杂。
英文摘要
(Abridged) In this work, we investigate the role of atomic hydrogen (HI) gas in the galaxy merger lifecycle. In order to both identify galaxies in mergers, as well as to predict their time since coalescence, we present an extension of the MUlti Model Merger Identifier (MUMMI) machine vision pipeline applied to Dark Energy Camera Legacy Survey (DECaLS) imaging. The new MUMMI-DECaLS catalog contains 19,951 post-mergers, of which 14,638 have robust time post-merger (T_PM) predictions. The MUMMI-DECaLS post-merger galaxy catalog is cross-matched with the Arecibo Legacy Fast ALFA (ALFALFA) survey. For the 752 post-mergers thus identified, as well as a matched control sample, we produce median spectral stacks of 21~cm emission, finding that the post-mergers are HI deficient by 0.11 dex compared with non-interacting galaxies. When divided into T_PM bins we find that the HI deficit (or excess) is strongly dependent on both the time since coalescence and whether the galaxies are star-forming or quenched. Star-forming post-mergers in particular show a strong HI evolution with T_PM, exhibiting a 0.1 dex MHI excess immediately after coalescence, a 0.3 dex MHI deficit at 0.16 < T_PM < 0.96 Gyr and normal gas masses by ~ 1.5 Gyr after coalescence. On the other hand, despite being matched in star formation rate, stellar mass and redshift, quenched post-mergers are HI deficient at both short and long post-coalescence times. Nonetheless, a significant mass of HI (>10^9 M_sun) remains even in these late-time quenched post-mergers, representing a resource which could potentially re-fuel star formation in the future. Our results demonstrate the complexity of quantifying the HI behaviour in mergers, which depends not only on timing, but also star-forming status, which can complicate comparisons between different studies and samples.
CommentsTo be submitted to the Open Journal of Astrophysics
