arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0901.3269astro-ph.CO
收藏

宇宙剪切可能性的非高斯性-或者：钱德拉深场南部有多奇怪？

The non-Gaussianity of the cosmic shear likelihood - or: How odd is the Chandra Deep Field South?

J. Hartlap, T. Schrabback, P. Simon, P. Schneider

备注：
18 pages, 16 figures, accepted for publication in A&A; New Bayesian treatment of field selection bias
发表信息：
Astron.Astrophys. 504:689-703,2009
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

我们研究了高斯宇宙剪切似然近似的有效性。我们估计真实的可能性，从一个大的射线追踪模拟的基准宇宙模型和宇宙学参数估计的非高斯性的影响进行调查。我们研究了最近报道的非常低的$σ_8$值是多么奇怪，因为它是从使用宇宙切变的\textit{Chandra}深场南方（CDFS）得出的，考虑到可能性的非高斯性以及CDFS选择方式带来的偏差的可能性。我们发现，宇宙剪切的可能性是显着的非高斯。这导致后验分布的最大值的偏移和与高斯情况相比显著更小的可信区域。我们重新分析CDFS宇宙剪切数据使用非高斯似然。假设CDFS是一个随机指向，我们发现$σ_8=0.68_{-0.16}^{+0.09}$固定$Ω_{\rm m}=0.25$。在类似WMAP 5的宇宙学中，在$\approx 5%$的时间中，期望值等于或小于这个值。考虑到偏差所产生的方式的CDFS的选择，我们的模型依赖于在CDFS中的晕的数量，我们得到$σ_8 = 0.71^{+0.10}_{-0.15}$。将CDFS数据与WMAP 5的参数约束相结合，得到了平坦宇宙的$Ω_{\rm m} = 0.26^{+0.03}_{-0.02}$和$σ_8 = 0.79^{+0.04}_{-0.03}$。

英文摘要：

(abridged) We study the validity of the approximation of a Gaussian cosmic shear likelihood. We estimate the true likelihood for a fiducial cosmological model from a large set of ray-tracing simulations and investigate the impact of non-Gaussianity on cosmological parameter estimation. We investigate how odd the recently reported very low value of $σ_8$ really is as derived from the \textit{Chandra} Deep Field South (CDFS) using cosmic shear by taking the non-Gaussianity of the likelihood into account as well as the possibility of biases coming from the way the CDFS was selected. We find that the cosmic shear likelihood is significantly non-Gaussian. This leads to both a shift of the maximum of the posterior distribution and a significantly smaller credible region compared to the Gaussian case. We re-analyse the CDFS cosmic shear data using the non-Gaussian likelihood. Assuming that the CDFS is a random pointing, we find $σ_8=0.68_{-0.16}^{+0.09}$ for fixed $Ω_{\rm m}=0.25$. In a WMAP5-like cosmology, a value equal to or lower than this would be expected in $\approx 5%$ of the times. Taking biases into account arising from the way the CDFS was selected, which we model as being dependent on the number of haloes in the CDFS, we obtain $σ_8 = 0.71^{+0.10}_{-0.15}$. Combining the CDFS data with the parameter constraints from WMAP5 yields $Ω_{\rm m} = 0.26^{+0.03}_{-0.02}$ and $σ_8 = 0.79^{+0.04}_{-0.03}$ for a flat universe.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑