小场调制CMB偏振实验中的绘图：近似极大似然方法
Map-making in small field modulated CMB polarisation experiments: approximating the maximum-likelihood method
摘要：
地图制作提出了一个重大的计算挑战，下一代千像素CMB偏振实验。来自数千个探测器的数年时间有序数据（TOD）需要压缩到T、Q和U斯托克斯参数的地图中。这些实验的科学目标的基础，B模式的观察，是控制噪声和系统学的能力。在本文中，我们考虑一种替代的极大似然的方法，称为striping，其中的噪声被建模为一组离散的偏移函数，然后从时间流中减去。我们比较我们的striping代码（Descart：DEStriping CARTographer）的一个完整的极大似然地图制造商，将它们应用到200蒙特卡罗模拟的时间顺序的数据从地面，部分天空偏振调制实验。在这些模拟中，噪声由探测器或大气1/f噪声主导。利用这种噪声的功率谱的先验信息，我们产生T，Q和U的striped映射，这些映射与最优映射的差异可以忽略不计。该方法不过滤信号或偏置E或B模式功率谱。根据不同的长度的踩基线，该方法提供了5和22倍之间的改进，在计算时间的极大似然算法。我们发现，对于单探测器地图的特定情况下，它是必不可少的stripe大气1/f，以检测B模式，即使Q和U信号调制的半波片旋转在5 Hz。
英文摘要：
Map-making presents a significant computational challenge to the next generation of kilopixel CMB polarisation experiments. Years worth of time ordered data (TOD) from thousands of detectors will need to be compressed into maps of the T, Q and U Stokes parameters. Fundamental to the science goal of these experiments, the observation of B-modes, is the ability to control noise and systematics. In this paper, we consider an alternative to the maximum-likelihood method, called destriping, where the noise is modelled as a set of discrete offset functions and then subtracted from the time-stream. We compare our destriping code (Descart: the DEStriping CARTographer) to a full maximum-likelihood map-maker, applying them to 200 Monte-Carlo simulations of time-ordered data from a ground based, partial-sky polarisation modulation experiment. In these simulations, the noise is dominated by either detector or atmospheric 1/f noise. Using prior information of the power spectrum of this noise, we produce destriped maps of T, Q and U which are negligibly different from optimal. The method does not filter the signal or bias the E or B-mode power spectra. Depending on the length of the destriping baseline, the method delivers between 5 and 22 times improvement in computation time over the maximum-likelihood algorithm. We find that, for the specific case of single detector maps, it is essential to destripe the atmospheric 1/f in order to detect B-modes, even though the Q and U signals are modulated by a half-wave plate spinning at 5-Hz.
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