We present a publicly-available code to generate sets of mock Lyman-α (Lyα) forest data that have realistic large-scale correlations including those due to the Baryonic Acoustic Oscillations (BAO). The primary purpose of these mocks is to test the analysis procedures of the Extended Baryon Oscillation Survey (eBOSS) and the Dark Energy Spectroscopy Instrument (DESI) surveys. The transmitted flux fraction, F(λ), of background quasars due to Lyα absorption in the intergalactic medium (IGM) is simulated using the Fluctuating Gunn-Petterson Approximation (FGPA) applied to Gaussian random fields produced through the use of fast Fourier transforms (FFT). The output includes the IGM-Lyα transmitted flux fraction along quasar lines of sight and a catalog of high-column-density systems appropriately placed at high-density regions of the IGM. This output serves as input to additional code that superimposes the IGM tranmission on realistic quasar spectra, adds absorption by high-column-density systems and metals, and simulates instrumental transmission and noise. Redshift space distortions (RSD) of the flux correlations are implemented by including the large-scale velocity-gradient field in the FGPA resulting in a correlation function of F(λ) that can be accurately predicted. One hundred realizations have been produced over the 14,000 deg² DESI survey footprint with 100 quasars per deg². The analysis of these realizations shows that the correlations of F(λ) follows the prediction within the accuracy of eBOSS survey. The most time-consuming part of the mock production occurs before application of the FGPA, and the existing pre-FGPA forests can be used to easily produce new mock sets with modified redshift-dependent bias parameters or observational conditions.

中文翻译：

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Eboss 和 DESI Lyman-α 森林调查的模拟数据集


我们提出了一个公开可用的代码来生成模拟莱曼α（Lyα）森林数据集，这些数据具有现实的大规模相关性，包括由重子声学振荡（BAO）引起的相关性。这些模拟的主要目的是测试扩展重子振荡勘测 (eBOSS) 和暗能量光谱仪器 (DESI) 勘测的分析程序。由于星际介质 (IGM) 中 Lyα 吸收而导致的背景类星体的透射通量分数 F(λ) 使用波动 Gunn-Petterson 近似 (FGPA) 进行模拟，该近似应用于通过使用快速傅里叶变换产生的高斯随机场 (快速傅里叶变换）。输出包括沿着类星体视线的 IGM-Lyα 传输通量分数以及适当放置在 IGM 高密度区域的高柱密度系统的目录。该输出作为附加代码的输入，将 IGM 传输叠加在真实的类星体光谱上，增加高柱密度系统和金属的吸收，并模拟仪器传输和噪声。通过在 FGPA 中包含大规模速度梯度场来实现通量相关性的红移空间畸变 (RSD)，从而产生可以准确预测的 F(λ) 相关函数。已在 14,000 度 ² DESI 勘测足迹上实现了一百个实现，每度 100 个类星体 ² 。对这些实现的分析表明，F(λ) 的相关性符合 eBOSS 调查精度范围内的预测。模拟生成中最耗时的部分发生在应用 FGPA 之前，并且可以使用现有的 FGPA 前森林轻松生成具有修改的红移相关偏差参数或观测条件的新模拟集。