Spectroscopic Identification of a Protocluster at z = 2.300: Environmental Dependence of Galaxy Properties at High Redshift
Spectroscopic Identification of a Protocluster at z = 2.300: Environmental Dependence of Galaxy Properties at High Redshift
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DOI：
10.1086/429989
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发表时间：
2005-02
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影响因子：
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通讯作者：
C. Steidel;K. Adelberger;A. Shapley;D. Erb;N. Reddy;M. Pettini
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作者：
C. Steidel;K. Adelberger;A. Shapley;D. Erb;N. Reddy;M. Pettini
在一次红移观测过程中，我们发现了非常显著的星系密度过高，其目的是在明亮的z=2.72类星体HS1700+643的视场中选择红移范围为z=2.3±0.4的恒星形成星系。该结构的红移空间星系超密度为δ≃7，实空间物质超密度估计为δm≃1.8，表明它将以≃1.4×1015M☉的质量标度z~0进行维尼化，这是一个丰富星系团的质量尺度。对这一领域中72个光谱确认的星系的光谱能量分布--从静止框架的远紫外到静止框架的近红外--进行了详细的建模，我们已经获得了它们的Ks和Spitzer IRAC光度学，这使得我们能够第一次直接比较星系的性质作为高红移大尺度环境的函数。我们发现，原星系团环境中的星系具有平均恒星质量和推断的年龄，它们比结构外相同的紫外线选择星系大~2倍(在z=2.30)，我们表明这与简单的理论预期是一致的，即在一个按观测量在大尺度上过度致密的区域，结构形成的加速。原星系团环境包含了相当数量的星系，这些星系看起来已经很老了，恒星质量很大(>；1011M☉)，z=2.3.
We have discovered a highly significant overdensity of galaxies at z = 2.300 ± 0.015 in the course of a redshift survey designed to select star-forming galaxies in the redshift range z = 2.3 ± 0.4 in the field of the bright z = 2.72 QSO HS 1700+643. The structure has a redshift-space galaxy overdensity of δ ≃ 7 and an estimated matter overdensity in real space of δm ≃ 1.8, indicating that it will virialize by z ~ 0 with a mass scale of ≃1.4 × 1015 M☉, that of a rich galaxy cluster. Detailed modeling of the spectral energy distribution—from the rest-frame far-UV to the rest-frame near-IR—of the 72 spectroscopically confirmed galaxies in this field for which we have obtained Ks and Spitzer IRAC photometry allows for a first direct comparison of galaxy properties as a function of large-scale environment at high redshift. We find that galaxies in the protocluster environment have mean stellar masses and inferred ages that are ~2 times larger (at z = 2.30) than identically UV-selected galaxies outside of the structure, and we show that this is consistent with simple theoretical expectations for the acceleration of structure formation in a region that is overdense on large scales by the observed amount. The protocluster environment contains a significant number of galaxies that already appear old, with large stellar masses (>1011 M☉), by z = 2.3.