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arXiv 1911.07855astro-ph.CO
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我们的局部环境对宇宙统计的影响

Impact of our local environment on cosmological statistics

Alex Hall

摘要:

我们进行了彻底的调查,居住在宇宙的过密区域可能会导致偏差的大尺度结构的测量的可能性。我们计算的条件关联函数和角功率谱的密度和透镜波动,同时保持当地的球平均密度固定,并表明,高斯场,这对角功率在$l>0$没有影响。我们确定了一个范围内的尺度,微扰的方法允许分析的进展,我们计算领先的顺序条件功率谱使用埃奇沃思展开和二阶微扰理论。我们没有发现任何显着的偏见,从我们的本地密度对比的宇宙学功率谱的证据。我们发现,当在观察者周围的一个大区域平滑时,局部密度的条件通常会影响密度功率谱,在宇宙学距离处,低于宇宙方差的百分比。我们发现,虽然典型的校正透镜角功率谱可以在10%的水平上的最大角尺度和源红移$z_s \lesssim 0.1$,为典型的红移为目标的即将到来的广泛的成像调查的校正是分百分比和可忽略不计,在文献中以前的索赔。使用估计的本地球形平均密度从复合星系红移目录,我们发现,我们自己的本地密度调节的校正低于宇宙方差和次主导的其他非线性效应。我们讨论了我们的研究结果对宇宙学的潜在影响,并指出,局部密度对比度的测量可用作宇宙学模型的一致性检验。

英文摘要:

We conduct a thorough investigation into the possibility that residing in an overdense region of the Universe may induce bias in measurements of the large-scale structure. We compute the conditional correlation function and angular power spectrum of density and lensing fluctuations while holding the local spherically averaged density fixed and show that for Gaussian fields this has no effect on the angular power at $l>0$. We identify a range of scales where a perturbative approach allows analytic progress to be made, and we compute leading-order conditional power spectra using an Edgeworth expansion and second-order perturbation theory. We find no evidence for any significant bias to cosmological power spectra from our local density contrast. We show that when smoothed over a large region around the observer, conditioning on the local density typically affects density power spectra by less than a percent at cosmological distances, below cosmic variance. We find that while typical corrections to the lensing angular power spectrum can be at the 10% level on the largest angular scales and for source redshifts $z_s \lesssim 0.1$, for the typical redshifts targeted by upcoming wide imaging surveys the corrections are sub-percent and negligible, in contrast to previous claims in the literature. Using an estimate of the local spherically averaged density from a composite galaxy redshift catalogue we find that the corrections from conditioning on our own local density are below cosmic variance and subdominant to other non-linear effects. We discuss the potential implications of our results for cosmology and point out that a measurement of the local density contrast may be used as a consistency test of cosmological models.

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