银河系环境测量- III。z ~ 2处原星系团识别的困难
Measures of Galaxy Environment - III. Difficulties in identifying proto-clusters at z ~ 2
摘要：
银河环境经常被讨论，但定义不一致。在只有光度红移的情况下，测量高红移特别困难。重点是早期形成的原星系团，我们使用半解析模型的星系形成，以显示如何高红移星系周围的环境测量是敏感的尺度和度量，以及集群的视角，演化状态，无论是光谱或光度数据的可用性。我们使用两种类型的环境指标（最近邻和固定孔径）在模拟高z集群的尺度范围内，看看如何“观察到的”overdensities比较“真正的”overdensities。我们还“观测”确定z = 2原集群候选人在我们的模型和跟踪其母晕的增长历史，通过时间，特别是考虑到他们的最终状态在z = 0。虽然早期形成的星团的测量环境严重依赖于所有上述效应（特别是视角），但我们发现这样的星团很可能（< 90%）在z = 0时保持过密，尽管许多将不再是最大的。然而，使用不同的方法和不同的数据进行实物比较需要更加谨慎。
英文摘要：
Galaxy environment is frequently discussed, but inconsistently defined. It is especially difficult to measure at high redshift where only photometric redshifts are available. With a focus on early forming proto-clusters, we use a semi-analytical model of galaxy formation to show how the environment measurement around high redshift galaxies is sensitive to both scale and metric, as well as to cluster viewing angle, evolutionary state, and the availability of either spectroscopic or photometric data. We use two types of environment metrics (nearest neighbour and fixed aperture) at a range of scales on simulated high-z clusters to see how "observed" overdensities compare to "real" overdensities. We also "observationally" identify z = 2 proto-cluster candidates in our model and track the growth histories of their parent halos through time, considering in particular their final state at z = 0. Although the measured environment of early forming clusters is critically dependent on all of the above effects (and in particular the viewing angle), we show that such clusters are very likely (< 90%) to remain overdense at z = 0, although many will no longer be among the most massive. Object to object comparisons using different methodologies and different data, however, require much more caution.
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