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arXiv 1008.0469astro-ph.COgr-qc
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在LTB宇宙中的CMB观测:第一部分:在LTB宇宙中的kSZ效应

CMB observations in LTB universes: Part II: the kSZ effect in an LTB universe

Chul-Moon Yoo, Ken-ichi Nakao, Misao Sasaki

摘要:

本文研究了LTB宇宙模型中的运动学Sunyaev-Zel'dovich(kSZ)效应,该模型的距离-红移关系在红移$z\lesssim2$处与协调$Λ$ CDM模型一致.这个LTB宇宙模型有一个大小与哈勃视界尺度相当的空洞。我们首先在对退耦时刻的物理量作了一些简化假设的情况下,通过近似解析条件确定了LTB宇宙模型的退耦时刻。然后计算了在LTB宇宙模型的空间同动坐标系中静止星系团静止坐标系中观测到的宇宙微波背景各向异性。我们发现所得到的温度各向异性是由偶极子主导的,虽然可能存在较高的多极一般。我们可以把这种偶极各向异性解释为星系团相对于宇宙微波背景静止坐标系的漂移速度。因此,它产生了kSZ效应。我们计算了这种影响,并将其与观测数据进行了比较。我们发现,如果我们假设传统的绝热扰动方案在去耦时,星系团的漂移速度变得不可接受的大。相反,可以通过引入非绝热(即,原始等曲率)分量。然而,我们的结果表明,所需的等曲率扰动幅度是非常大的。

英文摘要:

We study the kinematic Sunyaev-Zel'dovich (kSZ) effect in a Lemître-Tolman-Bondi (LTB) universe model whose distance-redshift relation agrees with that of the concordance $Λ$CDM model at redshifts $z\lesssim2$. This LTB universe model has a void with size comparable to the Hubble horizon scale. We first determine the decoupling epoch in this LTB universe model by an approximate analytical condition under a few simplified assumptions on the physical quantities at that epoch. Then we calculate the cosmic microwave background (CMB) anisotropy observed in the rest frame of clusters of galaxies which are assumed to be at rest in the spatial comoving coordinates of the LTB universe model. We find that the obtained temperature anisotropies are dominated by dipole, although there may exist higher multi-poles in general. We may interpret this dipole anisotropy as the drift velocity of a cluster of galaxies relative to the CMB rest frame. Hence it gives rise to the kSZ effect. We calculate this effect and compare it with observational data. We find that if we assume the conventional adiabatic perturbation scenario at the time of decoupling, the drift velocity of clusters of galaxies becomes unacceptably large. Conversely, this observational constraint may be relaxed by introducing a non-adiabatic (i.e., primordially isocurvature) component of inhomogeneities at the time of decoupling. However, our result indicates that the necessary isocurvature perturbation amplitude is very large.

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。

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