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arXiv 2005.05346astro-ph.COastro-ph.GA
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$z\sim 2$上IGM的三点和两点空间相关性：基于云的模拟分析

Three- and two-point spatial correlations of IGM at $z\sim 2$: Cloud based analysis using simulations

Soumak Maitra, Raghunathan Srianand, Prakash Gaikwad, Tirthankar Roy Choudhury, Aseem Paranjape, Patrick Petitjean

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26 pages, 23 figures. Submitted to MNRAS
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摘要：

Ly $α$森林吸收光谱分解成多个Voigt配置文件组件（云）允许我们研究星系际介质（IGM）作为HI柱密度（$N_{\rm HI}$）的函数的集群。在这里，我们探索横向三点相关（$ζ$）的这些LY $α$云使用模拟三重态光谱从流体动力学模拟在$z \sim 2$上的尺度为1-5 $h^{-1}$ cMpc。我们发现$ζ$强烈地依赖于$N_{\rm HI}$和尺度，弱地依赖于三重态构型的角度（$θ$）。我们表明，“层次分析法”是适用于尺度$\ge~ 3h^{-1}$ CMPC，并获得一个中位数减少三点相关性（Q）的范围为0.2-0.7。我们发现，$ζ$的强烈影响的热和电离状态的气体。在星系的情况下发现，物理参数对Q的影响比$ζ$的影响要弱。我们发现，如果我们使用适当的$N_{\rm HI}$截止对应于一个给定的重子过密度（$Δ$），使用测量的$N_{\rm HI}~vs~Δ$关系，从个人的模拟得到的不同的模拟之间的$ζ$和Q的差异最小化。此外，我们看到了压力增宽的影响$ζ$在一个模型与人为提高加热速率。然而，对于具有真实热历史和电离历史的模型，与其他局部效应相比，压力加宽对$ζ$的影响是弱的和次主导的。我们发现了由$ζ$表示的强烈的红移演化，主要来源于IGM热态和电离态的红移演化。我们讨论了三点相关检测的观测要求，特别是在小间隔的配置参数和红移。

英文摘要：

Ly$α$ forest absorption spectra decomposed into multiple Voigt profile components (clouds) allow us to study clustering of intergalactic medium (IGM) as a function of HI column density ($N_{\rm HI}$). Here, we explore the transverse three-point correlation ($ζ$) of these Ly$α$ clouds using mock triplet spectra obtained from hydrodynamical simulations at $z \sim 2$ on scales of 1-5 $h^{-1}$cMpc. We find $ζ$ to depend strongly on $N_{\rm HI}$ and scale and weakly on angle ($θ$) of the triplet configuration. We show that the "hierarchical ansatz" is applicable for scales $\ge~ 3h^{-1}$cMpc, and obtain a median reduced three-point correlation (Q) in the range 0.2-0.7. We show, $ζ$ is influenced strongly by the thermal and ionization state of the gas. As found in the case of galaxies, the influence of physical parameters on Q is weaker compared to that of $ζ$. We show difference in $ζ$ and Q between different simulations are minimized if we use appropriate $N_{\rm HI}$ cut-offs corresponding to a given baryon over-density ($Δ$) using the measured $N_{\rm HI}~vs~Δ$ relationship obtained from individual simulations. Additionally, we see the effect of pressure broadening on $ζ$ in a model with artificially boosted heating rates. However, for models with realistic thermal and ionization histories the effect of pressure broadening on $ζ$ is weak and sub-dominant compared to other local effects. We find strong redshift evolution shown by $ζ$, mainly originating from the redshift evolution of thermal and ionization state of the IGM. We discuss the observational requirements for the detection of three-point correlation, specifically, in small intervals of configuration parameters and redshift.

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