中等红移星系团内部的冷气体
Cold gas in the inner regions of intermediate redshift clusters
摘要：
场星系中气体含量和恒星形成率的测定已经取得了显著的进展，但在团内星系中的研究却少得多。本文首次对两个中等红移星系团CL 1416 +4446（z=0.397）和CL 0926 +1242（z=0.489）维里半径内的亮红外星系进行了CO观测。我们检测到三个星系在高的意义（5至10西格玛），并提供强大的估计，他们的CO光度，L 'CO。为了把我们的结果到一个一般的背景下，我们重新审视冷，热气体和恒星质量之间的关系在附近的领域和星系团星系。我们发现的证据表明，在固定的LIR（或固定的恒星质量），高L 'CO星系的频率是较低的集群比在外地，这表明环境枯竭的冷气体的水库。星系中恒星形成活动的水平主要与冷气体的数量有关，而不是与星系质量或回望时间有关。在星系团中，就像在磁场中一样，气体和恒星之间的转换似乎是普遍的。遥远星系团的LIR和L 'CO之间的关系将邻近星系的关系扩展到更高的红外光度。然而，中等红移的星系落在分散的趋势定义的本地系统。考虑到L 'CO一般来源于CO（1-0）线，对星系冷星际介质中的绝大多数分子气体敏感，而对实际用于形成恒星的部分却不敏感，我们建议在影响恒星形成率之前剥离分子气体。结合Geach et al.（2009，2011）和我们的样本，我们发现了CO向集群中心减少的证据。这是环境对中等红移的冷气体影响的第一个暗示。
英文摘要：
Determining gas content and star formation rate has known remarkable progress in field galaxies, but has been much less investigated in galaxies inside clusters. We present the first CO observations of luminous infrared galaxies (LIRGs) inside the virial radii of two intermediate redshift clusters, CL1416+4446 (z=0.397) and CL0926+1242 (z=0.489). We detect three galaxies at high significance (5 to 10 sigma), and provide robust estimates of their CO luminosities, L'CO. In order to put our results into a general context, we revisit the relation between cold and hot gas and stellar mass in nearby field and cluster galaxies. We find evidence that at fixed LIR (or fixed stellar mass), the frequency of high L'CO galaxies is lower in clusters than in the field, suggesting environmental depletion of the reservoir of cold gas. The level of star formation activity in a galaxy is primarily linked to the amount of cold gas, rather than to the galaxy mass or the lookback time. In clusters, just as in the field, the conversion between gas and stars seems universal. The relation between LIR and L'CO for distant cluster galaxies extends the relation of nearby galaxies to higher IR luminosities. Nevertheless, the intermediate redshift galaxies fall well within the dispersion of the trend defined by local systems. Considering that L'CO is generally derived from the CO(1-0) line and sensitive to the vast majority of the molecular gas in the cold interstellar medium of galaxies, but less to the part which will actually be used to form stars, we suggest that molecular gas can be stripped before the star formation rate is affected. Combining the sample of Geach et al. (2009, 2011) and ours, we find evidence for a decrease in CO towards the cluster centers. This is the first hint of an environmental impact on cold gas at intermediate redshift.
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