CMB constraint on non-Gaussianity in isocurvature perturbations
CMB constraint on non-Gaussianity in isocurvature perturbations
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DOI：
10.1088/1475-7516/2013/07/007
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发表时间：
2013
影响因子：
6.4
通讯作者：
Chiaki Hikage;Masahiro Kawasaki;Toyokazu Sekiguchi;Tomo Takahashi
中科院分区：
文献类型：
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作者：
Chiaki Hikage;Masahiro Kawasaki;Toyokazu Sekiguchi;Tomo Takahashi
我们研究了 CMB 等曲率扰动中非高斯性的约束。在宇宙的早期阶段，各种模型中都可以产生非高斯等曲率扰动。由于等曲率扰动对后期结构形成影响不大，因此至少在不久的将来，CMB 是等曲率非高斯性的最佳探针。在本文中，我们关注局部类型的非高斯曲率和等曲率扰动，它们是不相关的，形式为 ze = zeG+(3/5)fNL(zeG2−⟨zeG2⟩) 和 S = SG+fNL(ISO)(SG−⟨SG2⟩)，并约束等曲率扰动的非线性参数， fNL(ISO)，以及曲率一fNL。为此，我们采用了多种最先进的技术来分析 CMB 数据和模拟。假设等曲率扰动占主导地位，我们将我们的方法应用于 WMAP 7 年温度各向异性数据，并获得对组合 α2fNL(ISO) 的约束，其中 α 是等曲率扰动的功率谱与绝热扰动的功率谱之比。当假设绝热扰动为高斯扰动时，假设等曲率扰动的功率谱是尺度不变的，我们得到约束α2fNL(ISO) = 40±66。当我们假设绝热扰动也可以是非高斯时，我们得到 fNL = 38±24 和 α2fNL(ISO) = -8±72。我们还讨论了我们的结果对轴子 CDM 等曲率模型的影响。
We study the CMB constraints on non-Gaussianity in CDM isocurvature perturbations. Non-Gaussian isocurvature perturbations can be produced in various models at the very early stage of the Universe. Since the isocurvature perturbations little affect the structure formation at late times, CMB is the best probe of isocurvature non-Gaussianity at least in the near future. In this paper, we focus on non-Gaussian curvature and isocurvature perturbations of the local-type, which are uncorrelated and in the form ζ = ζG+(3/5)fNL(ζG2−⟨ζG2⟩) and S = SG+fNL(ISO)(SG−⟨SG2⟩), and constrain the non-linearity parameter of isocurvature perturbations, fNL(ISO), as well as the curvature one fNL. For this purpose, we employ several state-of-art techniques for the analysis of CMB data and simulation. Assuming that isocurvature perturbations are subdominant, we apply our method to the WMAP 7-year data of temperature anisotropy and obtain constraints on a combination α2fNL(ISO), where α is the ratio of the power spectrum of isocurvature perturbations to that of the adiabatic ones. When the adiabatic perturbations are assumed to be Gaussian, we obtained a constraint α2fNL(ISO) = 40±66 assuming the power spectrum of isocurvature perturbations is scale-invariant. When we assume that the adiabatic perturbations can also be non-Gaussian, we obtain fNL = 38±24 and α2fNL(ISO) = −8±72. We also discuss implications of our results for the axion CDM isocurvature model.