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arXiv 1310.2020astro-ph.CO
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SSA22 z=3.1原星系团中大质量星系的形成

The Formation of the massive galaxies in the SSA22 z=3.1 protocluster

Mariko Kubo, Yuka Katsuno Uchimoto, Toru Yamada, Masaru Kajisawa, Takashi Ichikawa, Yuichi Matsuda, Masayuki Akiyama, Tomoki Hayashino, Masahiro Konishi, Tetsuo… 展开作者

Mariko Kubo, Yuka Katsuno Uchimoto, Toru Yamada, Masaru Kajisawa, Takashi Ichikawa, Yuichi Matsuda, Masayuki Akiyama, Tomoki Hayashino, Masahiro Konishi, Tetsuo Nishimura, Koji Omata, Ryuji Suzuki, Ichi Tnaka, Tomohiro Yoshikawa, David. M. Alexander, Giovanni. G. Fazio, J. -S. Huang, Bret. D. Lehmer

摘要:

本文研究了z = 3.09SSA22原星系团场中K带选择星系(KAB <24)的性质。根据光度红移,在112弧分^[2]的区域内,选择了430个2.6 < z_phot < 3.6的星系作为潜在的原星系团成员。我们发现,在z_phot \sim 3.1恒星质量大于10 ^11 M_sun的大质量星系中,有\approx 20%的星系的颜色与年龄大于0.5 Gyr的静止星系的颜色一致。在校正不相关的前景/背景对象之后,该分数增加到\approx 50%。我们还发现,30%的大质量星系是严重变红的尘埃恒星形成星系。在典型的巡天中,很少能看到类似红移的静止星系。在z_phot \sim 3.1处还观测到24μm源的过剩面密度,这意味着在原星团中存在尘埃恒星形成活动。与X射线数据的交叉相关表明,K-波段选定的原团星系托管活动星系核(AGN)的分数也很高相比,该领域。静止星系、24μm源和X射线活动星系核的天空分布都显示出聚集在z=3.1的Lyα发射体(LAEs)密度峰周围。大质量星系中的相当一部分已经变得静止,而在SSA 22原星系团中,尘埃恒星的形成仍然活跃。这些发现表明,我们正在见证大质量早期型星系的形成时代,这些星系位于现代丰富星系团的前身中心。

英文摘要:

The properties of K-band selected galaxies (K_AB<24) in the z = 3.09 SSA22 protocluster field are studied. 430 galaxies at 2.6 < z_phot < 3.6 are selected as potential protocluster members in a 112 arcmin^2 area based on their photometric redshifts. We find that \approx 20% of the massive galaxies with stellar masses >10^11 M_sun at z_phot \sim 3.1 have colors consistent with those of quiescent galaxies with ages > 0.5 Gyr. This fraction increases to \approx 50% after correcting for unrelated foreground/background objects. We also find that 30% of the massive galaxies are heavily reddened dusty star-forming galaxies. Few such quiescent galaxies at similar redshifts are seen in typical survey fields. An excess surface density of 24μm sources at z_phot \sim 3.1 is also observed, implying the presence of dusty star-formation activity in the protocluster. Cross-correlation with the X-ray data indicates that the fraction of K-band selected protocluster galaxies hosting active galactic nuclei (AGN) is also high compared with the field. The sky distribution of the quiescent galaxies, the 24μm sources, and the X-ray AGNs show clustering around a density peak of z=3.1 Lyαemitters (LAEs). A significant fraction of the massive galaxies have already become quiescent, while the dusty star-formation is still active in the SSA22 protocluster. These findings indicate that we are witnessing the formation epoch of massive early-type galaxies at the center of predecessors to present-day rich galaxy clusters.

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