[论文解读] The DESI One-Percent Survey: Modelling the clustering and halo occupation of all four DESI tracers with Uchuu

Francisco Prada, J. Ereza+45 more|arXiv (Cornell University)|Jun 9, 2023

Galaxies: Formation, Evolution, Phenomena被引用 8

一句话总结

该论文基于高保真的 Uchuu 光锥，使用 SHAM 建模六 DESI 追踪体（BGS、LRG、ELG、QSO）的聚集和晕占据，覆盖 z=2.1，并将这些 mock 与 DESI One-Percent 数据进行比较以评估偏差和 HOD。

ABSTRACT

We present results from a set of mock lightcones for the DESI One-Percent Survey, created from the Uchuu simulation. This This 8 (Gpc/h)^3 N-body simulation comprises 2.1 trillion particles and provides high-resolution dark matter (sub)haloes in the framework of the Planck base-LCDM cosmology. Employing the subhalo abundance matching (SHAM) technique, we populate the Uchuu (sub)haloes with all four DESI tracers (BGS, LRG, ELG and QSO) to z = 2.1. Our method accounts for redshift evolution as well as the clustering dependence on luminosity and stellar mass. The two-point clustering statistics of the DESI One-Percent Survey generally agree with predictions from Uchuu across scales ranging from 0.3 Mpc/h to 100 Mpc/h for the BGS and across scales ranging from 5 Mpc/h to 100 Mpc/h for the other tracers. We observe some differences in clustering statistics that can be attributed to incompleteness of the massive end of the stellar mass function of LRGs, our use of a simplified galaxy-halo connection model for ELGs and QSOs, and cosmic variance. We find that at the high precision of Uchuu, the shape of the halo occupation distribution (HOD) of the BGS and LRG samples are not fully captured by the standard 5-parameter HOD model. However, the ELGs and QSOs show agreement with an adopted Gaussian distribution for central haloes with a power law for satellites. We observe fair agreement in the large-scale bias measurements between data and mock samples, although the BGS data exhibits smaller bias values, likely due to cosmic variance. The bias dependence on absolute magnitude, stellar mass and redshift aligns with that of previous surveys. These results provide DESI with tools to generate high-fidelity lightcones for the remainder of the survey and enhance our understanding of the galaxy-halo connection.

研究动机与目标

• 激励 DESI 需要理解星系–晕连接，以进行准确的宇宙学推断。
• 展示基于 Uchuu N-体模拟构建的四种 DESI 跟踪体的高保真 Mock 光锥。
• 量化不同追踪体与红移下的聚类与晕占据分布（HOD）。
• 评估基于 SHAM 的方法在再现 DESI One-Percent 聚类统计量和偏差方面的能力。

提出的方法

• 在 Planck 基于 ΛCDM 的 2.1 万亿颗粒 Uchuu N-body 模拟中创建 mock 光锥。
• 对 BGS-BRIGHT 和 LRG 跟踪体应用子晕丰度匹配（SHAM）以分配光度或恒星质量给（子）晕。
• 对于 ELG 与 QSO 跟踪体，采用修改后的 SHAM 方法以考虑不完整性和追踪体特定选择。
• 使用 V_peak 作为晕代理，拟合 ELG/QSO 的中心/卫星占据分布的高斯+幂律分布。
• 在 0.1 到 100 h^-1 Mpc 的尺度范围内，将获得的二点聚类和线性偏差与 DESI One-Percent 测量进行比较。

Figure 1: The sky coverage of the DESI One-Percent Survey for the BGS-BRIGHT, LRG, ELG, and QSO cosmological tracers used in this analysis. The 20 rosettes that make up the One-Percent footprint are split into ‘North’ (in black) and ‘South’ (in purple). The grey-shaded regions indicate the expected

实验结果

研究问题

• RQ1 SHAM 基于 Uchuu 晕的占据是否能再现四种追踪体（BGS、LRG、ELG、QSO）的 DESI One-Percent 聚类？
• RQ2 为匹配 DESI One-Percent 数据，每种追踪体所需的晕占据分布与偏差行为是什么？
• RQ3 ELG 与 QSO 的完整性与选择效应如何影响其 mock 人群与聚类？
• RQ4 尺度相关聚类差异是什么，对宇宙方差与星系–晕连接的意义为何？

主要发现

• 在 0.1–100 h^-1 Mpc 的尺度范围内，Uchuu mock 能较好地再现 DESI One-Percent 的追踪体。
• BGS 和 LRG 可以用标准的 5 参数 HOD 模型良好描述，而 ELG 与 QSO 需要一个中心高斯分布与卫星占据的幂律分布。
• Mock 与数据在大尺度偏差方面总体较为一致，数据偏差偏小可能归因于宇宙方差。
• 差异来自于宇宙方差、 massive 端恒星质量函数的不完整性，以及简化的星系–晕连接模型。
• 关于绝对星等、恒星质量和红移的偏差趋势与先前调查结果一致。
• 这些结果改进了来自宇宙学模型的光锥构造，并增进了对 DESI 的星系–晕连接理解。

Figure 2: The comoving number density of the four DESI One-Percent tracer samples (points) and the average of the corresponding high-fidelity Uchuu -DESI lighcones (solid line) over the entire redshift range $0.1<z<2.1$ . Data error bars are obtained from the ensemble of Uchuu One-Percent lighcones