部分贫气螺旋星系中的恒星形成
Star Formation in Partially Gas-Depleted Spiral Galaxies
摘要：
用智利Cerro Pachon山顶上的4.1米SOAR望远镜获得了飞马座I星系团中29个螺旋星系和非星系团环境中18个螺旋星系的宽带B和R以及H-α图像。飞马座I是一个富含螺旋的星团，具有低密度的团内介质和低的星系速度色散。结合Levy et al.（2007）和Springob et al.（2005 a）使用Arecibo 305-m射电望远镜获得的中性氢（HI）数据，我们研究了盘状星系中恒星形成率作为HI缺乏的函数。为了量化HI亏损，我们使用了常用的对数亏损参数DEF，用H-α通量与R带通量的对数通量比来量化比恒星形成率（SSFR），从而粗略地表征了单位恒星质量的对数SFR。我们发现一个明确的全球SFR每单位恒星质量和DEF之间的相关性，这样的SFR是更低的HI缺乏星系。这种相关性似乎从最富气体的星系延伸到最贫气体的星系。我们还发现，中央SFR每单位质量相对于全球价值观之间的相关性，在这个意义上说，更多的HI缺乏星系有一个更高的中央SFR每单位质量相对于他们的全球SFR值比气体丰富的星系。事实上，大约有一半的HI耗尽星系在其中心区域具有高度升高的SSFR，这表明了短暂的演化状态。此外，我们发现气体耗尽和H-α磁盘的大小（相对于R波段磁盘）之间的相关性; HI-贫穷的星系截断磁盘。此外，除了在许多贫气体螺旋星系中中央SSFR升高之外，在贫气体星系的H-α盘中SSFR比富气体螺旋星系低。
英文摘要：
Broadband B and R and H-alpha images have been obtained with the 4.1-m SOAR telescope atop Cerro Pachon, Chile for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (HI) data obtained with the Arecibo 305-m radiotelescope, acquired by Levy et al. (2007) and by Springob et al. (2005a), we study the star formation rates in disk galaxies as a function of their HI deficiency. To quantify HI deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of H-alpha flux to R band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more HI-deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more HI-deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the HI-depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas-depletion and the size of the H-alpha disk (relative to the R band disk); HI-poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the H-alpha disks of gas-poor galaxies than in gas-rich spirals.
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