Impact of modelling foreground uncertainties on future CMB polarization satellite experiments
Impact of modelling foreground uncertainties on future CMB polarization satellite experiments
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前景不确定性建模对未来 CMB 偏振卫星实验的影响
DOI：
10.1093/mnras/stx826
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发表时间：
2017
影响因子：
4.8
通讯作者：
Michael L. Brown
中科院分区：
文献类型：
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作者：
C. Herv'ias;A. Bonaldi;Michael L. Brown
我们提出了一个错误的张量标量比由于残留扩散前景的分析。我们使用模拟观测的CMB偏振卫星，宇宙起源探测器，使用2010年向欧空局提出的版本的规格（COrE）。我们构建了一个完整的管道，从微波天空地图$r$的可能性，使用两种模型的扩散银河前景不同的复杂性，并假设组件分离不同程度的准确性。我们的管道使用线性混合（广义最小二乘）解决方案的组件分离，和混合的方法进行功率谱估计，在低$\ell$s的二次最大似然估计和伪$C_{\ell}$反卷积在高$\ell$s。在$r$的可能性中，我们探索将前景残差建模为滋扰参数。我们的分析旨在测量的偏见引入的错误建模的前景，并确定什么样的错误是可以容忍的，同时仍然成功地检测$r$。我们发现，$r=0.01$，可以成功地测量，即使是一个复杂的天空模型，并在前景参数误差的存在。然而，$r=0.001$的检测更具挑战性，因为前景光谱特性的不准确建模可能导致$r$的有偏测量。一旦偏差被消除，$r$的总误差允许设置上限而不是检测，除非前景光谱指数的不确定性非常小，即等于或优于0.5%的灰尘和同步加速器的误差。这就强调了在下一代CMB偏振实验中进行组分分离和前景表征研究的必要性。
We present an analysis of errors on the tensor-to-scalar ratio due to residual diffuse foregrounds. We use simulated observations of a CMB polarization satellite, the Cosmic Origins Explorer, using the specifications of the version proposed to ESA in 2010 (COrE). We construct a full pipeline from microwave sky maps to $r$ likelihood, using two models of diffuse Galactic foregrounds with different complexity, and assuming component separation with varying degrees of accuracy. Our pipeline uses a linear mixture (Generalized Least Squares) solution for component separation, and a hybrid approach for power spectrum estimation, with a Quadratic Maximum Likelihood estimator at low $\ell$s and a pseudo-$C_{\ell}$ deconvolution at high $\ell$s. In the likelihood for $r$, we explore modelling foreground residuals as nuisance parameters. Our analysis aims at measuring the bias introduced in $r$ by mismodelling the foregrounds, and to determine what error is tolerable while still successfully detecting $r$. We find that $r=0.01$ can be measured successfully even for a complex sky model and in the presence of foreground parameters error. However, the detection of $r=0.001$ is a lot more challenging, as inaccurate modelling of the foreground spectral properties may result in a biased measurement of $r$. Once biases are eliminated, the total error on $r$ allows setting an upper limit rather than a detection, unless the uncertainties on the foreground spectral indices are very small, i.e. equal or better than 0.5\% error for both dust and synchrotron. This emphasizes the need for pursuing research on component separation and foreground characterization in view of next-generation CMB polarization experiments.