Super-Sample Signal
Super-Sample Signal
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DOI：
10.1103/physrevd.90.103530
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发表时间：
2014-08
影响因子：
5
通讯作者：
Yin Li;Wayne Hu;M. Takada
中科院分区：
文献类型：
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作者：
Yin Li;Wayne Hu;M. Takada
在从功率谱测量中提取宇宙学信息时，必须考虑波长大于观测尺度的超样本密度涨落的影响。这些模式导致了调查中的平均密度起伏，并以与宇宙学背景变化相同的方式改变了功率谱。它们可以简单地包括在宇宙学参数估计和预测中，方法是将$\deltab$作为一个额外的宇宙学参数，从而能够有效地探索其影响。为了测试这一方法，我们在这里考虑了物质功率谱本身在$\lambda$CDM宇宙学中的理想化测量，尽管我们的技术可以很容易地扩展到更具观测相关性的统计或其他参数空间。使用大体积$N$体模拟的子体积，无论是相对于全局平均密度还是局部平均密度测量的功率谱，我们验证了最小方差估计器$\Delta_b$是无偏的，并且具有预测的方差。参数简并是由于物质功率谱对β_b的响应引起的，宇宙学参数在改变结构的生长和扩大特征尺度方面具有相似的性质，特别是在局域情况下。对于物质功率谱测量，这些简并在某些情况下可能导致严重的误差退化，并推动未来使用这些技术对特定的宇宙学观测数据进行研究，如星系团和弱透镜统计。
When extracting cosmological information from power spectrum measurements, we must consider the impact of super-sample density fluctuations whose wavelengths are larger than the survey scale. These modes contribute to the mean density fluctuation $\delta_b$ in the survey and change the power spectrum in the same way as a change in the cosmological background. They can be simply included in cosmological parameter estimation and forecasts by treating $\delta_b$ as an additional cosmological parameter enabling efficient exploration of its impact. To test this approach, we consider here an idealized measurement of the matter power spectrum itself in the $\Lambda$CDM cosmology though our techniques can readily be extended to more observationally relevant statistics or other parameter spaces. Using sub-volumes of large-volume $N$-body simulations for power spectra measured with respect to either the global or local mean density, we verify that the minimum variance estimator of $\delta_b$ is both unbiased and has the predicted variance. Parameter degeneracies arise since the response of the matter power spectrum to $\delta_b$ and cosmological parameters share similar properties in changing the growth of structure and dilating the scale of features especially in the local case. For matter power spectrum measurements, these degeneracies can lead in certain cases to substantial error degradation and motivates future studies of specific cosmological observables such as galaxy clustering and weak lensing statistics with these techniques.