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arXiv 2104.13595astro-ph.CO
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通过星系剪切探测宇宙放大--来自HSC巡天数据的星系数密度关联

Detection of Cosmic Magnification via Galaxy Shear -- Galaxy Number Density Correlation from HSC Survey Data

Xiangkun Liu, Dezi Liu, Zucheng Gao, Chengliang Wei, Guoliang Li, Liping Fu, Toshifumi Futamase, Zuhui Fan

备注：
9 pages, 4 figures; Accepted for publication in PRD
发表信息：
Published in Physical Review D, Volume 103, Issue 12, p.123504, 2021
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摘要：

我们提出了一种新的方法来检测宇宙放大率信号的交叉相关的前景收敛场构造的星系剪切测量与背景星系的位置分布，即剪切数密度相关。我们将其应用于超级Suprime-Cam斯巴鲁战略计划（HSC-SSP）的调查数据。利用27个非独立数据点及其全协方差，分别计算了关于零值和宇宙学模型的$χ_0^2\approx 34.1$和$χ_T^2\approx 24.0$，参数来自Hamana et al. 2020（arXiv：1906.06041）中的HSC剪切相关分析。两者的贝叶斯因子是$\log_{10}B_{T0}\approx 2.2$，假设零和HSC宇宙学的模型概率相等，显示出放大信号的清晰检测。从理论上讲，剪切数密度和剪切相关性的比例可以提供一个约束的有效乘法剪切偏置$\bar m$使用内部数据本身。我们证明了我们的HSC-SSP模拟模拟信号的想法和重新调整的统计不确定性的调查$15000°^2$。对于背景星系比$m_{lim}=23$亮的双箱分析，组合分析导致预测的约束$σ(\bar m) \sim 0.032$，$2.3$倍紧比单独使用剪切-剪切相关。相应地，具有$S_8=σ_8(Ω_\mathrm{m}/0.3)^{0.5}$的$σ(S_8)$收紧$\sim 2.1$倍。重要的是，对$\bar m$的联合约束几乎与宇宙学参数无关。因此，我们的研究指出了在弱透镜分析中包括剪切数密度相关的重要性，这可以提供有价值的观测数据的一致性检验，从而巩固导出的宇宙学约束。

英文摘要：

We propose a novel method to detect cosmic magnification signals by cross-correlating foreground convergence fields constructed from galaxy shear measurements with background galaxy positional distributions, namely shear-number density correlation. We apply it to the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey data. With 27 non-independent data points and their full covariance, $χ_0^2\approx 34.1$ and $χ_T^2\approx 24.0$ with respect to the null and the cosmological model with the parameters from HSC shear correlation analyses in Hamana et al. 2020 (arXiv:1906.06041), respectively. The Bayes factor of the two is $\log_{10}B_{T0}\approx 2.2$ assuming equal model probabilities of null and HSC cosmology, showing a clear detection of the magnification signals. Theoretically, the ratio of the shear-number density and shear-shear correlations can provide a constraint on the effective multiplicative shear bias $\bar m$ using internal data themselves. We demonstrate the idea with the signals from our HSC-SSP mock simulations and rescaling the statistical uncertainties to a survey of $15000°^2$. For two-bin analyses with background galaxies brighter than $m_{lim}=23$, the combined analyses lead to a forecasted constraint of $σ(\bar m) \sim 0.032$, $2.3$ times tighter than that of using the shear-shear correlation alone. Correspondingly, $σ(S_8)$ with $S_8=σ_8(Ω_\mathrm{m}/0.3)^{0.5}$ is tightened by $\sim 2.1$ times. Importantly, the joint constraint on $\bar m$ is nearly independent of cosmological parameters. Our studies therefore point to the importance of including the shear-number density correlation in weak lensing analyses, which can provide valuable consistency tests of observational data, and thus to solidify the derived cosmological constraints.

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