DETECTING BARYON ACOUSTIC OSCILLATIONS
DETECTING BARYON ACOUSTIC OSCILLATIONS
复制标题
检测重子声振荡
DOI：
10.1088/0004-637x/746/2/172
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
M. Lachièze‐Rey
中科院分区：
文献类型：
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作者：
A. Labatie;J. Starck;M. Lachièze‐Rey
重子声振荡（BAO）是早期宇宙等离子体中传播的声波在星系分布中留下的特征。它们在大尺度结构中的预期尺度上的探测强烈支持了当前的宇宙学模型，该模型从红移z = 1000到暗能量的存在几乎是线性演化的。此外，BAO为研究宇宙膨胀提供了一个标准标尺。在本文中，我们专注于使用相关函数测量的BAO检测方法。对于每种方法，我们都想了解测试的假设（要拒绝的假设）和基本假设。我们首先提出了小波方法，这是温和的模型依赖性和最敏感的BAO功能。然后我们转向完全依赖模型的方法。我们提出了基于χ2统计量的最常用的方法，但我们发现它有局限性。一般情况下，χ2方法的假设没有得到验证，它只给出了显著性的粗略估计。当考虑更现实的假设时，估计可能会变得非常错误，其中的协方差矩阵取决于宇宙学参数。相反，我们建议使用基于两个修改的Δl方法：我们修改计算显著性的过程并使其严格，并且我们修改统计量以在变化协方差矩阵的情况下获得更好的结果。我们通过模拟验证了正确的显著性与使用经典χ2程序获得的显著性不同。我们还测试了一个简单的例子，不同的协方差矩阵。在这种情况下，我们发现，当两个显著性都被正确计算时，我们修改后的统计量优于经典的χ2统计量。最后，我们发现，考虑到协方差矩阵的变化可以改变两个BAO检测水平和宇宙学参数的约束。
Baryon acoustic oscillations (BAOs) are a feature imprinted in the galaxy distribution by acoustic waves traveling in the plasma of the early universe. Their detection at the expected scale in large-scale structures strongly supports current cosmological models with a nearly linear evolution from redshift z ≈ 1000 and the existence of dark energy. In addition, BAOs provide a standard ruler for studying cosmic expansion. In this paper, we focus on methods for BAO detection using the correlation function measurement . For each method, we want to understand the tested hypothesis (the hypothesis to be rejected) and the underlying assumptions. We first present wavelet methods which are mildly model-dependent and mostly sensitive to the BAO feature. Then we turn to fully model-dependent methods. We present the method used most often based on the χ2 statistic, but we find that it has limitations. In general the assumptions of the χ2 method are not verified, and it only gives a rough estimate of the significance. The estimate can become very wrong when considering more realistic hypotheses, where the covariance matrix of depends on cosmological parameters. Instead, we propose to use the Δl method based on two modifications: we modify the procedure for computing the significance and make it rigorous, and we modify the statistic to obtain better results in the case of varying covariance matrix. We verify with simulations that correct significances are different from the ones obtained using the classical χ2 procedure. We also test a simple example of varying covariance matrix. In this case we find that our modified statistic outperforms the classical χ2 statistic when both significances are correctly computed. Finally, we find that taking into account variations of the covariance matrix can change both BAO detection levels and cosmological parameter constraints.