[论文解读] Extensive analysis of reconstruction algorithms for DESI 2024 baryon acoustic oscillations

Xinyi Chen, Z. Ding+65 more|arXiv (Cornell University)|Nov 29, 2024

Galaxies: Formation, Evolution, Phenomena被引用 6

一句话总结

本文评估 DESI 2024 BAO 分析中的重建算法（MG、iFFT、iFFTP），覆盖 ELG、QSO 和 BGS 样本，推荐 MG/iFFT 搭配 RecSym，并强调 iFFTP 的问题。

ABSTRACT

Reconstruction of the baryon acoustic oscillation (BAO) signal has been a standard procedure in BAO analyses over the past decade and has helped to improve the BAO parameter precision by a factor of ~2 on average. The Dark Energy Spectroscopic Instrument (DESI) BAO analysis for the first year (DR1) data uses the ``standard'' reconstruction framework, in which the displacement field is estimated from the observed density field by solving the linearized continuity equation in redshift space, and galaxy and random positions are shifted in order to partially remove nonlinearities. There are several approaches to solving for the displacement field in real survey data, including the multigrid (MG), iterative Fast Fourier Transform (iFFT), and iterative Fast Fourier Transform particle (iFFTP) algorithms. In this work, we analyze these algorithms and compare them with various metrics including two-point statistics and the displacement itself using realistic DESI mocks. We focus on three representative DESI samples, the emission line galaxies (ELG), quasars (QSO), and the bright galaxy sample (BGS), which cover the extreme redshifts and number densities, and potential wide-angle effects. We conclude that the MG and iFFT algorithms agree within 0.4% in post-reconstruction power spectrum on BAO scales with the RecSym convention, which does not remove large-scale redshift space distortions (RSDs), in all three tracers. The RecSym convention appears to be less sensitive to displacement errors than the RecIso convention, which attempts to remove large-scale RSDs. However, iFFTP deviates from the first two; thus, we recommend against using iFFTP without further development. In addition, we provide the optimal settings for reconstruction for five years of DESI observation. The analyses presented in this work pave the way for DESI DR1 analysis as well as future BAO analyses.

研究动机与目标

• 评估不同位移场重建方法如何影响 DESI BAO 分析。
• 使用真实的 DESI 模拟数据在多个示踪体（ELG、QSO、BGS）比较 MG、iFFT、iFFTP 算法。
• 评估重建公约（RecSym 与 RecIso）及位移误差对结果的敏感性。
• 为 DESI 五年的观测提供推荐的重建设置。

提出的方法

• 使用真实的 DESI 模拟数据比较三种位移场求解器（MG、iFFT、iFFTP）。
• 应用解线性连续方程在红移空间中的标准 BAO 重建框架。
• 在 RecSym 公约下评估重建后对 BAO 尺度的功率谱。
• 对比 RecSym 与 RecIso 公约在对位移误差的敏感性方面的差异。
• 为 DESI 五年的观测推导最优重建设置。

实验结果

研究问题

• RQ1 MG、iFFT 与 iFFTP 在 DESI 示踪体的重建后 BAO 功率谱中有何差异？
• RQ2 在位移误差存在时，哪种重建公约（RecSym vs RecIso）具有更鲁棒的结果？
• RQ3 在 ELG、QSO 与 BGS 样本的五年 DESI 数据中，最优的重建设置是什么？

主要发现

• 在 RecSym 下，对三种示踪体而言，MG 与 iFFT 在 BAO 尺度的重建后功率谱上一致性在 0.4% 以内。
• RecSym 公约对位移误差的敏感性低于 RecIso。
• iFFTP 与 MG 和 iFFT 偏离，且在未进一步开发前不推荐使用。
• 该研究为 DESI 五年的观测给出最优的重建设置。