Accurate Fourier-space statistics for line intensity mapping: Cartesian grid sampling without aliased power
Accurate Fourier-space statistics for line intensity mapping: Cartesian grid sampling without aliased power
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用于线强度映射的精确傅里叶空间统计：无混叠功率的笛卡尔网格采样
DOI：
10.1093/mnras/stae333
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发表时间：
2024
影响因子：
4.8
通讯作者：
Cunnington S
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文献类型：
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作者：
Cunnington S
在傅里叶空间中，基于点聚类统计的估计量要求将大型结构的现代测量转换为笛卡尔坐标来进行快速傅里叶变换（FFTs）。在这项工作中，我们在像素化线强度图（LIM）的背景下探讨了这种转换，强调了对功率谱测量的潜在偏置影响。目前的分析经常通过将测量几何近似为笛卡尔空间中的矩形来避免对数据进行完全重新采样，这对于现代宽天空测量来说是一个越来越不准确的假设。我们对21厘米LIM调查的模拟表明，这一假设对所有尺度的功率谱测量都有偏差。因此，我们提出了一个更强大的框架，通过对大量蒙特卡罗采样粒子进行坐标变换，将体素强度重新划分到3D FFT场。虽然这在大尺度上消除了功率谱测量的偏差，但较小尺度的差异仍然存在，这是由网格未解决的分离引起的结构平滑和混叠造成的。为了纠正这些影响，我们引入了建模技术、高阶粒子分配和交错FFT网格来抑制混叠功率。使用分段三次样条（PCS）粒子分配和交错FFT场，我们在21厘米LIM模拟中实现了高达80%奈奎斯特频率的亚%精度。我们发现，相对于星系巡天所取得的成果，高阶分配方案的结果有了更微妙的层次改进，我们将其归因于LIM中额外离散步骤带来的额外复杂性。本文附带的Pythoncode可从github.com/stevecunnington/gridimp获得。
Estimators forn-point clustering statistics in Fourier-space demand that modern surveys of large-scale structure be transformed to Cartesian coordinates to perform Fast Fourier Transforms (FFTs). In this work, we explore this transformation in the context of pixelized line intensity maps (LIM), highlighting potential biasing effects on power-spectrum measurements. Current analyses often avoid a complete resampling of the data by approximating survey geometry as rectangular in Cartesian space, an increasingly inaccurate assumption for modern wide-sky surveys. Our simulations of a21 cm LIM survey atshow this assumption biases power-spectrum measurements byacross all scales. We therefore present a more robust framework for regridding the voxel intensities on to a 3D FFT field by coordinate transforming large numbers of Monte-Carlo sampling particles. Whilst this unbiases power-spectrum measurements on large scales, smaller scale discrepancies remain, caused by structure smoothing and aliasing from separations unresolved by the grid. To correct these effects, we introduce modelling techniques, higher order particle assignments, and interlaced FFT grids to suppress the aliased power. Using a piecewise cubic spline (PCS) particle assignment and an interlaced FFT field, we achieve sub-per cent accuracy up to 80 per cent of the Nyquist frequency for our 21 cm LIM simulations. We find a more subtle hierarchical improvement in results for higher order assignment schemes, relative to the gains made for galaxy surveys, which we attribute to the extra complexity in LIM from additional discretizing steps.pythoncode accompanying this paper is available at github.com/stevecunnington/gridimp.
“与组方案相关的角色产品和平衡集”（预印本）。
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