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arXiv 2302.08515astro-ph.CO
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BOSS LOWZ星系所追踪的大尺度结构是否与Planck一致？

Is the large-scale structure traced by the BOSS LOWZ galaxies consistent with $\textit{Planck}$?

Zhiwei Shao, Ying Zu, Huanyuan Shan

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8 pages, 5 figures, comments welcome!
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AI总结：

本研究构建线性理论模型评估BOSS LOWZ星系成团与透镜效应在Planck宇宙学下的差异，通过交叉相关诊断排除系统误差，并利用星系团弱透镜独立测量打破参数简并，最终证实其大尺度结构与Planck一致。

摘要：

最近，几项研究报告指出，在Planck宇宙学下，重子振荡光谱巡天（BOSS）星系的成团与引力透镜效应之间存在显著差异。我们构建了一个基于线性理论的简单而强大的模型，以评估这种差异是否意味着偏离了Planck。聚焦于10<R<30 h⁻¹Mpc的尺度，我们使用三个参数对BOSS LOWZ星系的成团和透镜振幅进行建模：星系偏置b_g、星系-物质交叉相关系数r_gm，以及A（定义为真实σ_8值与Planck值之比）。利用交叉相关矩阵作为诊断工具，我们检测到了导致低质量星系间产生虚假相关的系统不确定性。在构建了r_gm~1的纯净LOWZ样本后，我们通过成团+透镜效应推导出b_g和A的联合约束，得到b_g=2.47⁺⁰·³⁶₋₀.₃₀和A=0.81⁺⁰·¹⁰₋₀.₀₉，即与Planck存在2σ的张力。然而，由于b_g和A之间存在强简并性，b_g的系统不确定性可能伪装成与A=1的张力。为确定这种可能性，我们开发了一种新方法，利用重叠星系团样本，通过星系团-星系交叉相关和星系团弱引力透镜来测量b_g。通过将独立的偏置测量值（b_g=1.76±0.22）作为先验，我们成功打破了简并性，并推导出严格的约束：b_g=2.02⁺⁰·¹⁶₋₀.₁₅和A=0.96±0.07。因此，我们的结果表明，LOWZ星系的大尺度成团和透镜效应与Planck是一致的，而不同的偏置估计可能与目标选择中的某些观测系统误差有关。

英文摘要：

Recently, several studies reported a significant discrepancy between the clustering and lensing of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxies in the $\textit{Planck}$ cosmology. We construct a simple yet powerful model based on the linear theory to assess whether this discrepancy points toward deviations from $\textit{Planck}$. Focusing on scales $10<R<30$ $h^{-1}\mathrm{Mpc}$, we model the amplitudes of clustering and lensing of BOSS LOWZ galaxies using three parameters: galaxy bias $b_\mathrm{g}$, galaxy-matter cross-correlation coefficient $r_\mathrm{gm}$, and $A$, defined as the ratio between the true and $\textit{Planck}$ values of $σ_8$. Using the cross-correlation matrix as a diagnostic, we detect systematic uncertainties that drive spurious correlations among the low-mass galaxies. After building a clean LOWZ sample with $r_\mathrm{gm}\sim1$, we derive a joint constraint of $b_\mathrm{g}$ and $A$ from clustering+lensing, yielding $b_\mathrm{g}=2.47_{-0.30}^{+0.36}$ and $A=0.81_{-0.09}^{+0.10}$, i.e., a $2σ$ tension with $\textit{Planck}$. However, due to the strong degeneracy between $b_\mathrm{g}$ and $A$, systematic uncertainties in $b_\mathrm{g}$ could masquerade as a tension with $A=1$. To ascertain this possibility, we develop a new method to measure $b_\mathrm{g}$ from the cluster-galaxy cross-correlation and cluster weak lensing using an overlapping cluster sample. By applying the independent bias measurement ($b_\mathrm{g}=1.76\pm0.22$) as a prior, we successfully break the degeneracy and derive stringent constraints of $b_\mathrm{g}=2.02_{-0.15}^{+0.16}$ and $A=0.96\pm0.07$. Therefore, our result suggests that the large-scale clustering and lensing of LOWZ galaxies are consistent with $\textit{Planck}$, while the different bias estimates may be related to some observational systematics in the target selection.

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