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arXiv 2006.09368astro-ph.COastro-ph.GA
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星系偏差和原始非高斯性:来自IllustrisTNG星系形成模拟的见解

Galaxy bias and primordial non-Gaussianity: insights from galaxy formation simulations with IllustrisTNG

Alexandre Barreira, Giovanni Cabass, Fabian Schmidt, Annalisa Pillepich, Dylan Nelson

摘要:

利用IllustrisTNG模型研究了物质密度和原初引力势的大尺度扰动对星系形成的影响.我们重点讨论了线性星系偏差$b_1$和由PNG引起的尺度相关偏差系数$b_ϕ$,它们分别描述了星系数计数对这两种扰动的响应。我们进行我们的研究,使用单独的宇宙模拟,其中的扰动的影响是模仿宇宙学参数的变化:修改后的宇宙物质密度为$b_1$和修改后的振幅$\mathcal{A}_s$的原始标量功率谱$b_ϕ$。我们发现,广泛使用的普适关系$b_ϕ= 2δ_c(b_1 - 1)$是一个穷人的描述晕和星系选择恒星质量$M_*$的偏见,这是相反的描述更好的$b_ϕ(M_*) = 2δ_c(b_1(M_*) - p)$与$p \in [0.4, 0.7]$。这是由物质过密度和局部PNG对恒星与晕质量关系中值的不同影响所解释的。一个简单的模型,这种影响使我们能够描述恒星质量依赖的$b_1$和$b_ϕ$相当不错。我们的结果还表明,对于由颜色和黑洞质量吸积率选择的星系,$b_1$和$b_ϕ$之间存在非平凡的关系。我们的研究结果提供了完善的先验$b_ϕ$本地PNG的限制和预测,使用星系聚类。鉴于广泛使用的普适性关系低估了$b_ϕ(M_*)$,现有的分析可能低估了本地PNG的真正约束力。

英文摘要:

We study the impact that large-scale perturbations of (i) the matter density and (ii) the primordial gravitational potential with local primordial non-Gaussianity (PNG) have on galaxy formation using the IllustrisTNG model. We focus on the linear galaxy bias $b_1$ and the coefficient $b_ϕ$ of the scale-dependent bias induced by PNG, which describe the response of galaxy number counts to these two types of perturbations, respectively. We perform our study using separate universe simulations, in which the effect of the perturbations is mimicked by changes to the cosmological parameters: modified cosmic matter density for $b_1$ and modified amplitude $\mathcal{A}_s$ of the primordial scalar power spectrum for $b_ϕ$. We find that the widely used universality relation $b_ϕ= 2δ_c(b_1 - 1)$ is a poor description of the bias of haloes and galaxies selected by stellar mass $M_*$, which is instead described better by $b_ϕ(M_*) = 2δ_c(b_1(M_*) - p)$ with $p \in [0.4, 0.7]$. This is explained by the different impact that matter overdensities and local PNG have on the median stellar-to-halo-mass relation. A simple model of this impact allows us to describe the stellar mass dependence of $b_1$ and $b_ϕ$ fairly well. Our results also show a nontrivial relation between $b_1$ and $b_ϕ$ for galaxies selected by color and black hole mass accretion rate. Our results provide refined priors on $b_ϕ$ for local PNG constraints and forecasts using galaxy clustering. Given that the widely used universality relation underpredicts $b_ϕ(M_*)$, existing analyses may underestimate the true constraining power on local PNG.

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