Red galaxy overdensities and the varied cluster environments of powerful radio sources with z~1.6
Red galaxy overdensities and the varied cluster environments of powerful radio sources with z~1.6
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红星系密度过大和 z~1.6 强射电源的不同星团环境
DOI：
10.1046/j.1365-8711.2003.06667.x
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发表时间：
2003
影响因子：
4.8
通讯作者：
H. Rottgering
中科院分区：
文献类型：
--
作者：
P.N.Best;M.D.Lehnert;G. Miley;H. Rottgering
利用深度为R ~（26）、J ~（22.4）和K ~（20.6）的RJK深成像，研究了6个最强射电噪的活动星系核（AGN）在红移z ~（1.6）处的完整子样本的环境。在这些区域中可以看到K波段的星系数量过多;这些过剩的星系数量主要与在AGN宿主的径向距离为100万秒差距内发现的17.5 K 20.5等的红星系（R-K 4）有关。这些都是（虽然不是唯一的）的大小，颜色和位置，将预期在这些活动星系核的红移星系团环境中的旧被动椭圆星系。使用阿贝尔式的分类方案和调查的角度和空间的互相关函数的星系，这些活动星系核周围的领域的平均环境被发现是一致的阿贝尔集群丰富类0和1。的幅度的角互相关函数周围的活动星系核被证明是一个强大的功能的星系的颜色和最高时，只有那些星系的颜色预期的老椭圆星系在这些红移被认为是。这些图像覆盖了一个相对较宽的视场，5 × 5 arcmin 2，允许研究剩余星系计数的分布。星系超密度在活动星系核周围的两个尺度上被发现：（i）在150 kpc以内的径向尺度上有明显的中心集中;在存在的地方，这些星系几乎完全由红色（R-K 4）星系组成，这表明形态-密度关系在高红移时被印在星系团的中心;（ii）较弱的大尺度超密度延伸到1到1.5-Mpc半径之间。然而，在这两个尺度上是否存在星系过剩，在六个不同的场之间有很大的不同：两个活动星系核的场在两个尺度上都显示出红色星系过剩，另外两个场只显示出大尺度的红色星系过密度，没有明显的中心集中，一个场只显示出红色星系的尖锐中心峰，没有大尺度的过密度。最后一个字段显示在任何规模的过剩的证据很少，这个字段是与一个未解决的无线电源，也许表明，只有扩展的无线电源探测集群环境。
The environments of a complete subsample of six of the most powerful radio-loud active galactic nuclei (AGN) at redshifts z ∼ 1.6 are investigated, using deep RJK imaging to depths of R ∼ 26, J ∼ 22.4 and K ∼ 20.6. An excess of galaxy counts in the K band is seen across these fields; these surplus galaxy counts are predominantly associated with red galaxies (R − K 4) of magnitudes 17.5 K 20.5 found within radial distances of ∼1 Mpc of the AGN host. These are exactly (though not uniquely) the magnitudes, colours and locations that would be expected of old passive elliptical galaxies in cluster environments at the redshifts of these AGN. Using both an Abell-style classification scheme and investigations of the angular and spatial cross-correlation functions of the galaxies, the average environment of the fields around these AGN is found to be consistent with Abell cluster richness classes 0 and 1. The amplitude of the angular cross-correlation function around the AGN is shown to be a strong function of galaxy colour and is highest when only those galaxies with the colours expected of old elliptical galaxies at these redshifts are considered. The images cover a relatively wide field, 5 × 5 arcmin 2 , allowing the distribution of the surplus galaxy counts to be investigated. The galaxy overdensities are found on two scales around the AGN: (i) pronounced central concentrations on radial scales within ∼150 kpc; where present, these are composed almost entirely of red (R − K 4) galaxies, suggesting that the morphology‐density relation is imprinted into the centres of clusters at a high redshift; (ii) weaker large-scale excesses extending out to between 1 and 1.5-Mpc radius. The presence or absence of galaxy excesses on these two scales, however, differs greatly between the six different fields: the fields of two AGN do show red galaxy excesses on both scales, another two fields show only a large-scale red galaxy overdensity with no pronounced central concentration, and one field shows only a sharp central peak of red galaxies with no large-scale overdensity. The final field shows little evidence for an excess on any scale; this field is associated with an unresolved radio source, perhaps indicating that only extended radio sources probe cluster environments.