全景H-alpha映射揭示的z=2.16原星系团中的大质量星暴星系
Massive starburst galaxies in a z=2.16 proto-cluster unveiled by panoramic H-alpha mapping
摘要：
我们提出了一个全景窄带研究的H-α发射场的z=2.16原星系团周围PKS 1138 -262使用MOIRCS的斯巴鲁望远镜。我们发现了83个H-α发射体，其SFR（Ha）约为10 Msun/yr，分布在以射电星系为中心的~ 7 'x7'区域，并确定了~10-Mpc尺度的发射体细丝。通过研究大尺度结构中H-α发射体的性质，我们发现z=2.16的高密度环境中的星系与密度较低区域的星系相比，往往具有更红的颜色和更高的恒星质量。我们还发现了一群红色的H-α发射体（（J-Ks）>1），它们在稠密的环境中更常见，并且具有明显很高的恒星质量，M*>~10^11Msun，这意味着这些星系团在z~2之前就已经形成了它们的大部分恒星质量。斯皮策太空望远镜24微米的数据表明，这些红色的H-α发射体中有许多是明亮的尘埃星暴（而不是静止的源）。我们还发现原星系团星系遵循同样的SFR与z~2场成星星系的M*（“主序列”）之间的相关性，但大质量星系过剩。这些非常巨大的恒星形成星系在我们以前对z~1星系团的类似研究中没有看到，这表明它们的恒星形成活动在1<~z<~2时已经关闭。我们推测，在这个丰富的原星系团中的大质量红色（但活跃的）星系很可能是环境效应的产物，它们代表了宇宙早期偏高密度区加速的星系形成和演化。
英文摘要：
We present a panoramic narrow-band study of H-alpha emitters in the field of the z=2.16 proto-cluster around PKS1138-262 using MOIRCS on the Subaru Telescope. We find 83 H-alpha emitters down to a SFR(Ha)~10Msun/yr across a ~7'x7' region centered on the radio galaxy, and identify ~10-Mpc scale filaments of emitters running across this region. By examining the properties of H-alpha emitters within the large-scale structure, we find that galaxies in the higher-density environments at z=2.16 tend to have redder colours and higher stellar masses compared to galaxies in more underdense regions. We also find a population of H-alpha emitters with red colours ((J-Ks)>1), which are much more frequent in the denser environments and which have apparently very high stellar masses with M*>~10^11Msun, implying that these cluster galaxies have already formed a large part of their stellar mass before z~2. Spitzer Space Telescope 24-micron data suggests that many of these red H-alpha emitters are bright, dusty starbursts (rather than quiescent sources). We also find that the proto-cluster galaxies follow the same correlation between SFR and M* (the "main sequence") of z~2 field star-forming galaxies, but with an excess of massive galaxies. These very massive star-forming galaxies are not seen in our similar, previous study of z~1 clusters, suggesting that their star-formation activity has been shut off at 1<~z<~2. We infer that the massive red (but active) galaxies in this rich proto-cluster are likely to be the products of environmental effects, and they represent the accelerated galaxy formation and evolution in a biased high density region in the early Universe.
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