模拟星系成团和星系-星系透镜进入深度非线性区域：方法、信息和预报
Emulating galaxy clustering and galaxy-galaxy lensing into the deeply nonlinear regime: methodology, information, and forecasts
摘要：
将星系-星系透镜效应（GGL）与星系成团效应相结合是确定低红移物质成团振幅的最有前途的途径之一。我们发现，扩展聚类+GGL分析从线性制度下到$\sim 0.5 \, h^{-1}$ Mpc尺度大大增加了他们的约束力，即使在边缘化的非线性星系偏差的灵活模型。使用网格的宇宙学N体模拟，我们构建了一个泰勒膨胀模拟器，预测星系的自相关$ξ_{\text{gg}}(r)$和星系物质的互相关$ξ_{\text{gm}}(r)$作为$σ_8$，$Ω_m$，和晕占据分布（HOD）参数的函数，这是允许随大尺度环境而变化，以代表可能的影响星系组装偏差。我们给出了对应于BOSS LOWZ星系聚集和SDSS深度弱透镜（有效源密度$\sim 0.3$ arcmin $^{-2}$）的基准案例的预测。在$0.5 \leq r_p \leq 30 \, h^{-1}$ Mpc上使用切向剪切和投影相关函数测量，对参数组合$σ_8Ω_m^{0.58}$产生1.8%的约束，比排除非线性尺度的约束（$γ_t,w_p$的$r_p > 2 \, h^{-1}$ Mpc、$4 \, h^{-1}$ Mpc）好两倍。这种改进大部分来自非线性聚类信息，它打破了HOD参数之间的退化，否则会降低从GGL的物质聚类的推断。将有效源密度增加到$3$ arcmin $^{-2}$使对$σ_8Ω_m^{0.58}$的约束进一步增加两倍。通过对非线性区域的鲁棒建模，仅使用聚类+GGL在1%水平上对物质聚类的低红移测量完全可以达到当前的数据集，例如暗能量调查提供的数据集。
英文摘要：
The combination of galaxy-galaxy lensing (GGL) with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low redshifts. We show that extending clustering+GGL analyses from the linear regime down to $\sim 0.5 \, h^{-1}$ Mpc scales increases their constraining power considerably, even after marginalizing over a flexible model of non-linear galaxy bias. Using a grid of cosmological N-body simulations, we construct a Taylor-expansion emulator that predicts the galaxy autocorrelation $ξ_{\text{gg}}(r)$ and galaxy-matter cross-correlation $ξ_{\text{gm}}(r)$ as a function of $σ_8$, $Ω_m$, and halo occupation distribution (HOD) parameters, which are allowed to vary with large scale environment to represent possible effects of galaxy assembly bias. We present forecasts for a fiducial case that corresponds to BOSS LOWZ galaxy clustering and SDSS-depth weak lensing (effective source density $\sim 0.3$ arcmin$^{-2}$). Using tangential shear and projected correlation function measurements over $0.5 \leq r_p \leq 30 \, h^{-1}$ Mpc yields a 1.8% constraint on the parameter combination $σ_8Ω_m^{0.58}$, a factor of two better than a constraint that excludes non-linear scales ($r_p > 2 \, h^{-1}$ Mpc, $4 \, h^{-1}$ Mpc for $γ_t,w_p$). Much of this improvement comes from the non-linear clustering information, which breaks degeneracies among HOD parameters that would otherwise degrade the inference of matter clustering from GGL. Increasing the effective source density to $3$ arcmin$^{-2}$ sharpens the constraint on $σ_8Ω_m^{0.58}$ by a further factor of two. With robust modeling into the non-linear regime, low-redshift measurements of matter clustering at the 1-percent level with clustering+GGL alone are well within reach of current data sets such as those provided by the Dark Energy Survey.
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