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arXiv 1303.4307astro-ph.CO
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星暴后星系的冷气体含量

The cold gas content of post-starburst galaxies

Martin A. Zwaan, Harald Kuntschner, Michael B. Pracy, Warrick J. Couch

摘要:

星暴后星系,或称E+A星系,其特征是光谱显示出强烈的巴耳末吸收线,表明有一个年轻的恒星星族,而很少或没有发射线,意味着没有活跃的恒星形成。这些星系被解释为恒星形成,盘主导的星系和球状静止,非恒星形成星系之间的过渡人口。在这里,我们提出了单盘HI 21厘米发射线测量的样本中的11个星系在红移z<0.05。我们在六个E+A星系中探测到H I发射。结合早期的研究,现在有测量到冷气体成分的E+A星系的总数是11个。到目前为止,大约有一半的E+As研究有可检测的HI。这些星系的气体分数,相对于它们的恒星质量测量,在1%和10%之间,并且在含气体的早期类型星系中测量的气体分数的高端,通常低于具有可比恒星质量的晚期类型星系。这一发现与E+As目前正从蓝色云向红色序列演变的想法一致。然而,为什么这些星系中的恒星形成已经停止,而大量的气体储存仍然存在,这个问题只能通过对冷气体的更高空间分辨率的观测来回答。

英文摘要:

Post-starburst galaxies, or E+A galaxies, are characterized by optical spectra showing strong Balmer absorption lines, indicating a young stellar population, and little or no emission lines, implying no active star formation. These galaxies are interpreted as a transitional population between star-forming, disk-dominated galaxies and spheroidal quiescent, non-star forming galaxies. Here, we present single dish HI 21-cm emission line measurements of a sample of eleven of these galaxies at redshifts z<0.05. We detect H I emission in six of the E+A galaxies. In combination with earlier studies, the total number of E+A galaxies with measured cold gas components is now eleven. Roughly half of the E+As studied so far have detectable HI. The gas fractions of these galaxies, measured with respect to their stellar mass, are between 1 and 10 percent and are at the high end of the gas fractions measured in gas-bearing early type galaxies and typically lower than seen in late-type galaxies with comparable stellar masses. This finding is consistent with the idea that E+As are currently evolving from the blue cloud to the red sequence. However, the question of why the star formation has ceased in these galaxies while a significant gas reservoir is still present can only be answered by higher spatial resolution observations of the cold gas.

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