arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2011.02475astro-ph.COastro-ph.IM
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无仪器噪声偏置的CMB透镜功率谱估计

CMB lensing power spectrum estimation without instrument noise bias

Mathew S. Madhavacheril, Kendrick M. Smith, Blake D. Sherwin, Sigurd Naess

摘要:

宇宙微波背景(CMB)透镜的功率谱将在即将进行的调查中测量到低于%的精度,从而严格限制中微子质量和其他宇宙学参数的总和。测量透镜功率谱涉及CMB图的四点函数的连接三谱的估计,这需要减去大的高斯断开噪声偏置。这种重建噪声偏差受到CMB和前景波动以及仪器噪声(地面勘测的探测器噪声和大气噪声)的影响。因此,去偏置过程依赖于仪器噪声的模拟质量,这可能是昂贵的或不准确的。我们提出了一个新的估计,利用至少四个分裂的CMB地图与独立的仪器噪声。该估计器使得CMB透镜功率谱对在建模或模拟仪器噪声中做出的任何假设完全不敏感。我们表明,这种估计,在许多实际情况下,导致信号噪声没有实质性的损失。我们提供了一个有效的算法,其计算,规模与分裂$m$的数量为$\mathcal{O}(m^2)$,而不是一个天真的$\mathcal{O}(m^4)$的期望。

英文摘要:

The power spectrum of cosmic microwave background (CMB) lensing will be measured to sub-percent precision with upcoming surveys, enabling tight constraints on the sum of neutrino masses and other cosmological parameters. Measuring the lensing power spectrum involves the estimation of the connected trispectrum of the four-point function of the CMB map, which requires the subtraction of a large Gaussian disconnected noise bias. This reconstruction noise bias receives contributions both from CMB and foreground fluctuations as well as instrument noise (both detector and atmospheric noise for ground-based surveys). The debiasing procedure therefore relies on the quality of simulations of the instrument noise which may be expensive or inaccurate. We propose a new estimator that makes use of at least four splits of the CMB maps with independent instrument noise. This estimator makes the CMB lensing power spectrum completely insensitive to any assumptions made in modeling or simulating the instrument noise. We show that this estimator, in many practical situations, leads to no substantial loss in signal-to-noise. We provide an efficient algorithm for its computation that scales with the number of splits $m$ as $\mathcal{O}(m^2)$ as opposed to a naive $\mathcal{O}(m^4)$ expectation.

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