利用半解析星系形成模型结合宇宙学N体模拟,对Λ冷暗物质宇宙中极红天体(ERO)的成簇进行了预测. ERO是在0.7< z < 3观测到的红色大质量星系,它们的数量和性质对分层星系形成模型提出了挑战。分析了ERO的晕占据分布和两点关联函数,探讨了这些量随视星等、色切和红移的变化规律。我们的模型预测的晕占据分布是显着不同的,通常假设。这是由于活动星系核反馈的加入,它改变了活动星系核反馈第一次变得重要的质量之上的亮度-宿主晕质量关系的斜率和散射。我们预测,平均而言,质量大于10^{13}h^{-1}Msun的暗物质晕至少有一个在1.5 < z < 2.5处的ERO。考虑到观测估计中的样本方差,对于(R-K)>5或(i-K)>4.5的ERO,预测的角聚类与当前观测结果相当一致。
英文摘要:
We present predictions for the clustering of Extremely Red Objects (EROs) in a Λcold dark matter Universe, using a semi-analytical galaxy formation model in combination with a cosmological N-body simulation. EROs are red, massive galaxies observed at 0.7< z < 3, and their numbers and properties have posed a challenge to hierarchical galaxy formation models. We analyse the halo occupation distribution and two-point correlation function of EROs, exploring how these quantities change with apparent magnitude, colour cut and redshift. Our model predicts a halo occupation distribution that is significantly different from that typically assumed. This is due to the inclusion of AGN feedback, which changes the slope and scatter of the luminosity-host halo mass relation above the mass where AGN feedback first becomes important. We predict that, on average, dark matter haloes with masses above 10^{13}h^{-1}Msun host at least one ERO at 1.5 < z < 2.5. Taking into account sample variance in observational estimates, the predicted angular clustering for EROs with either (R-K)>5 or (i-K)>4.5 is in reasonable agreement with current observations.
Anisotropic effective redshift and evolving clustering amplitude
一个典型的星系巡天几何学会导致不同间距和视线角度的星系对具有不同的红移分布,从而产生不同的有效红移。然而,聚类测量分析假设的聚类是在一个单一的有效红移的代表。我们调查的影响,在星系对有效红移的大规模集群测量星系巡天的变化。我们发现,星系调查跨越一个大的红移范围有不同的有效红移作为一个函数的对分离和角度。此外,当考虑示踪剂的聚类幅度随红移强烈演变时,这种组合可以导致额外的尺度依赖的聚类各向异性。我们证明了这种影响的大小的eBOSS DR 16类星体样本,并表明,虽然对磁的影响是可以忽略不计的,忽略这种影响可能会导致大规模的倾斜$\sim 4\%$和$\sim40\%$在四极和十六极,分别。我们讨论的策略,以减轻这种影响时,进行测量。
Redshift-space distortions in the clustering of galaxy clusters provide a novel probe to test the gravity theory on cosmological scales. The aim of this work is to derive new constraints on the linear growth rate of cosmic structures from the redshift-space two-point correlation function of galaxy clusters. We construct a large spectroscopic catalogue of optically-selected clusters from the Sloan Digital Sky Survey. The selected sample consists of $43,743$ clusters in the redshift range $0.1<z<0.42$, with masses estimated from weak-lensing calibrated scaling relations. We measure the transvers…
Analytical tools are extremely hard to find for non-linear gravitational collpase. Only a few simple but powerful tools exist so far. Two examples are the spherical collapse model (SCM) and stable clustering hypothesis (SCH). We present a new analytical tool, a two-body collapse model (TBCM), that plays the same fundamental role as harmonic oscillator in dynamics. For convenience, TBCM is formulated for gravity with any potential exponent $n$ in a static background with a fixed damping ($n$=-1 for Newtonian gravity). The competition between gravity, expanding background (or damping), and angul…