Characterising and identifying galaxy protoclusters
Characterising and identifying galaxy protoclusters
复制标题
DOI：
10.1093/mnras/stx3090
复制
发表时间：
2017-10
影响因子：
4.8
通讯作者：
C. Lovell;P. Thomas;S. Wilkins
中科院分区：
文献类型：
--
作者：
C. Lovell;P. Thomas;S. Wilkins
我们利用最新的L-GALAXIES半解析模型研究了星系原星系团的特征。在~ 10 cMpc的尺度上寻找原星系团，在星系群的完整性和纯度之间取得了很好的折衷，导致了与过密度空间中的场的高度区分，并允许精确确定后代星系团的质量。该刻度在一系列红移和选择标准上有效。我们提出了一种程序，在给定测量的星系过密度的情况下，根据一系列建模假设，特别是考虑到测量孔径的形状，估计原星团的概率及其后代星团的质量。与先前使用固定孔径的估计相比，该程序产生更低的原星团概率。研究了活动星系核（AGN）与原星系团之间的关系，并显示出随着红移的显著演化；在z ~ 2时，AGN追踪的原团簇比例较高，但所有AGN在原团簇中的比例较低，而在atz≥5时，含有AGN的原团簇比例较低，但大多数AGN都在原团簇中。我们还发现了间接证据，证明在z ~ 2的原星系团中出现了被动序列，并注意到所有星系中有很大一部分位于z≥2的原星系团中，特别是质量最大的。
We study the characteristics of galaxy protoclusters using the latest L-GALAXIES semi-analytic model. Searching for protoclusters on a scale of ∼10 cMpc gives an excellent compromise between the completeness and purity of their galaxy populations, leads to high distinction from the field in overdensity space, and allows accurate determination of the descendant cluster mass. This scale is valid over a range of redshifts and selection criteria. We present a procedure for estimating, given a measured galaxy overdensity, the protocluster probability and its descendant cluster mass for a range of modelling assumptions, particularly taking into account the shape of the measurement aperture. This procedure produces lower protocluster probabilities compared to previous estimates using fixed size apertures. The relationship between active galactic nucleus (AGN) and protoclusters is also investigated and shows significant evolution with redshift; at z ∼ 2, the fraction of protoclusters traced by AGN is high, but the fraction of all AGNs in protoclusters is low, whereas atz ≥ 5 the fraction of protoclusters containing AGN is low, but most AGNs are in protoclusters. We also find indirect evidence for the emergence of a passive sequence in protoclusters at z ∼ 2, and note that a significant fraction of all galaxies reside in protoclusters at z ≥ 2, particularly the most massive.