最佳周期性搜索：重温大尺度脉冲星巡天的快速折叠算法
Optimal periodicity searching: Revisiting the Fast Folding Algorithm for large-scale pulsar surveys
摘要：
快速折叠算法（FFA）是一种用于周期信号的相位相干搜索技术。它很少用于射电脉冲星搜索，历史上被计算成本较低的快速傅里叶变换（FFT）和非相干谐波求和（IHS）所取代。在这里，我们从第一原则，FFA搜索接近理论上的最佳灵敏度，所有周期性信号，它被分析表明是显着更敏感的比标准的FFT+IHS方法，无论脉冲周期和占空比。因此，脉冲星相空间的一部分已经系统地探索了几十年;脉冲星调查，旨在充分采样的脉冲星人口应包括FFA搜索作为其数据分析的一部分。我们已经开发了FFA软件包，激流，足够快，以处理大规模的无线电观测;激流已经发现了使用现有的FFT+IHS实现检测不到的来源。我们的搜索技术之间的灵敏度比较也表明，需要一个更现实的辐射计方程，其中包括一个额外的术语：搜索效率。我们推导出FFA和FFT+IHS方法的理论效率，并讨论如何排除这一项脉冲星人口合成研究的后果。
英文摘要：
The Fast Folding Algorithm (FFA) is a phase-coherent search technique for periodic signals. It has rarely been used in radio pulsar searches, having been historically supplanted by the less computationally expensive Fast Fourier Transform (FFT) with incoherent harmonic summing (IHS). Here we derive from first principles that an FFA search closely approaches the theoretical optimum sensitivity to all periodic signals; it is analytically shown to be significantly more sensitive than the standard FFT+IHS method, regardless of pulse period and duty cycle. A portion of the pulsar phase space has thus been systematically under-explored for decades; pulsar surveys aiming to fully sample the pulsar population should include an FFA search as part of their data analysis. We have developed an FFA software package, riptide, fast enough to process radio observations on a large scale; riptide has already discovered sources undetectable using existing FFT+IHS implementations. Our sensitivity comparison between search techniques also shows that a more realistic radiometer equation is needed, which includes an additional term: the search efficiency. We derive the theoretical efficiencies of both the FFA and the FFT+IHS methods and discuss how excluding this term has consequences for pulsar population synthesis studies.
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