[论文解读] The Pantheon+ Analysis: Cosmological Constraints

Dillon Brout, D. Scolnic+44 more|Edinburgh Research Explorer|Feb 8, 2022

Cosmology and Gravitation Theories被引用 20

一句话总结

Pantheon+ 分析了 1701 条 Type Ia 超新星光曲线（1550 个超新星）以在改进的系统误差下约束宇宙学，获得仅 SN 的以及与外部数据联合约束的 H0 和暗能量参数，包括 w0 和 wa。

ABSTRACT

We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from $z=0.001$ to 2.26. This work features an increased sample size, increased redshift span, and improved treatment of systematic uncertainties in comparison to the original Pantheon analysis and results in a factor of two improvement in cosmological constraining power. For a Flat$Λ$CDM model, we find $Ω_M=0.334\pm0.018$ from SNe Ia alone. For a Flat$w_0$CDM model, we measure $w_0=-0.90\pm0.14$ from SNe Ia alone, H$_0=73.5\pm1.1$ km s$^{-1}$ Mpc$^{-1}$ when including the Cepheid host distances and covariance (SH0ES), and $w_0=-0.978^{+0.024}_{-0.031}$ when combining the SN likelihood with constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both $w_0$ values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a Flat$w_0w_a$CDM universe, and measure $w_a=-0.1^{+0.9}_{-2.0}$ from Pantheon+ alone, H$_0=73.3\pm1.1$ km s$^{-1}$ Mpc$^{-1}$ when including SH0ES, and $w_a=-0.65^{+0.28}_{-0.32}$ when combining Pantheon+ with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one third of the total uncertainty in the measurement of H$_0$ and cannot explain the present "Hubble tension" between local measurements and early-Universe predictions from the cosmological model.

研究动机与目标

• 通过跨校准光度测量扩展 SN Ia 宇宙学数据集并扩展红移覆盖范围。
• 将校准、光曲线拟合、红移与偏差校正等方面的系统误差传播与建模。
• 同时利用 SN 数据独立以及外部先验（SH0ES 造变星、Planck、BAO）约束宇宙学参数（Omega_M、w0、wa）以及哈勃常数。
• 评估 SN 系统误差对 H0 以及哈勃张力的影响。
• 发布数据、模拟以及协方差矩阵以实现可重复性与进一步分析。

提出的方法

• 通过 SALT2 光曲线拟合标准化 SN Ia 光度，得到 m_B、x1、c、t0。
• 使用类似 BBC 的估计量计算距离模量，包含 alpha、beta、gamma、delta_bias，以及宿主质量校正（delta_host）。
• 为 1701 条光曲线构建未分箱的统计与系统协方差矩阵以传播不确定性。
• 通过最小化带 C_stat+syst 的卡方来约束宇宙学，使用来自平坦或弯曲宇宙学的模型距离，H(z) 由 H0、Omega_M 和 w 参数描述。
• 纳入 SH0ES 造变星宿主距离及其协方差，以获得 SN+Cepheid 的联合约束，并与 Planck/BAO 的似然联合用于扩展模型。
• 进行“盲”分析，使用宇宙学隐藏残差及偏移的 CosmoSIS 链以防止偏差。

Figure 1: Analysis roadmap of this work and supporting/complementary Pantheon+ and SH0ES papers. Components of the analysis here are shown in blue. The companion paper R22, which provides a constraint on H 0 , requires the Hubble diagram and covariance computed in this work. Likewise, measurements o

实验结果

研究问题

• RQ1 Pantheon+ SN Ia 数据单独能得到的 Omega_M、w0、wa 的宇宙学约束是什么？
• RQ2 SN 系统误差和跨校准如何影响推断的 H0 和暗能量性质？
• RQ3 包含 SH0ES 造变星校准星对 H0 与膨胀历史的确定有何影响？
• RQ4 Planck 与 BAO 数据如何与 Pantheon+ 结合来约束平坦的 w0wa CDM 模型？
• RQ5 Pantheon+ 的结果在多种参数化下是否表明与宇宙常数一致？

主要发现

• 对于平坦 LambdaCDM，SN Ia 单独给出 Omega_M = 0.334 ± 0.018。
• 对于平坦 w0CDM，SN Ia 单独给出 w0 = -0.90 ± 0.14；结合 SH0ES 造变星宿主，H0 = 73.5 ± 1.1 km s^-1 Mpc^-1。
• 联合 SN+Planck+BAO，w0 = -0.978^{+0.024}_{-0.031}，与宇宙常数一致。
• 在平坦的 w0waCDM 中，Pantheon+ 单独得到 w0 wa = -0.1^{+0.9}_{-2.0}；带 SH0ES 时，H0 = 73.3 ± 1.1；带 Planck+BAO 时，w0 wa = -0.65^{+0.28}_{-0.32}。
• SN Ia 的系统性不确定性对 H0 的总不确定性贡献不到三分之一，不能解释当前的哈勃张力。
• 该分析在平坦的 w0waCDM 框架下给出了迄今为止最精确的暗能量演化测量。

Figure 2: Comparison between observed data (black points) and simulations (blue lines) for the largest subsamples in this analysis: DES, HST , SDSS, SNLS, PS1, LOW- $z$ , Foundation (FOUND). We compare three key distributions: the SALT2 light-curve-fit parameters $x_{1}$ and $c$ are shown as well as