[论文解读] A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team

Adam G. Riess, Wenlong Yuan+16 more|arXiv (Cornell University)|Dec 8, 2021

Gamma-ray bursts and supernovae被引用 194

一句话总结

本论文通过利用HST、Gaia以及maser/LMC/MW锚定，在42个SNe Ia宿主中分析Cephheids，给出局部H0的1 km/s/Mpc不确定性的确定值，并探索大量分析变体。

ABSTRACT

We report observations from HST of Cepheids in the hosts of 42 SNe Ia used to calibrate the Hubble constant (H0). These include all suitable SNe Ia in the last 40 years at z<0.01, measured with >1000 orbits, more than doubling the sample whose size limits the precision of H0. The Cepheids are calibrated geometrically from Gaia EDR3 parallaxes, masers in N4258 (here tripling that Cepheid sample), and DEBs in the LMC. The Cepheids were measured with the same WFC3 instrument and filters (F555W, F814W, F160W) to negate zeropoint errors. We present multiple verifications of Cepheid photometry and tests of background determinations that show measurements are accurate in the presence of crowding. The SNe calibrate the mag-z relation from the new Pantheon+ compilation, accounting here for covariance between all SN data, with host properties and SN surveys matched to negate differences. We decrease the uncertainty in H0 to 1 km/s/Mpc with systematics. We present a comprehensive set of ~70 analysis variants to explore the sensitivity of H0 to selections of anchors, SN surveys, z range, variations in the analysis of dust, metallicity, form of the P-L relation, SN color, flows, sample bifurcations, and simultaneous measurement of H(z). Our baseline result from the Cepheid-SN sample is H0=73.04+-1.04 km/s/Mpc, which includes systematics and lies near the median of all analysis variants. We demonstrate consistency with measures from HST of the TRGB between SN hosts and NGC 4258 with Cepheids and together these yield 72.53+-0.99. Including high-z SN Ia we find H0=73.30+-1.04 with q0=-0.51+-0.024. We find a 5-sigma difference with H0 predicted by Planck+LCDM, with no indication this arises from measurement errors or analysis variations considered to date. The source of this now long-standing discrepancy between direct and cosmological routes to determining the Hubble constant remains unknown.

研究动机与目标

• 通过尽量降低系统误差，用Cepheid–SN Ia距离梯来量化局部膨胀率H0。
• 用几何锚定（Gaia视差、NGC 4258masers、LMC DEBs）对Cepheid光度进行标定。
• 对SN Ia绝对光度及Hubble流动中的SN样本进行交叉标定，以推导H0。
• 通过评估约70种分析变体，涵盖锚、SN调查、红移范围以及尘埃/金属丰度处理，来评估鲁棒性。

提出的方法

• 提出一个三步距离梯，将Cepheid在SN Ia宿主中的距离与经过标定的SN Ia光度联系起来。
• 使用Wesenheit光度来去除Cepheid的红化，并将Cepheid光度建模为 mH^W = μ0 + MH,1^W + bW(log P − 1) + ZW[O/H]。
• 通过线代框架结合协方差感知的χ2目标函数，同时拟合H0、SN Ia光度和Cepheid标准化参数。
• incorporate几何距离先验（NGC 4258、MW、LMC），并包括SN数据与宿主性质之间的协方差。
• 将局部H0与高红移SN Ia约束进行比较，并可选地加入TRGB锚定以检验一致性。

实验结果

研究问题

• RQ1 使用扩展的Cepheid–SN Ia距离梯并结合广泛锚定后，局部H0的值是多少？
• RQ2 几何锚定（Gaia、NGC 4258、LMC）和SN系统误差如何影响H0的不确定性和中心值？
• RQ3 所得H0与基于TRGB的估计以及Planck ΛCDM预测的一致性如何？
• RQ4 H0对锚点选择、尘埃/金属丰度处理、P-L关系形式以及SN拟合变体有多鲁棒？
• RQ5 在推断膨胀历史（q0）和H0时，包含高红移SNe Ia的影响是什么？

主要发现

• Cepheid–SN Ia样本的基线H0为73.04 ± 1.04 km s−1 Mpc−1（含系统误差）。
• 包含TRGB锚定得到H0 = 72.53 ± 0.99 km s−1 Mpc−1。
• 包含高红移SNe Ia得到H0 = 73.30 ± 1.04 km s−1 Mpc−1，且q0 = −0.51 ± 0.024。
• 结果显示与Planck CMB ΛCDM预测存在约5σ的差异，且未见证明该差异来自于测量不确定性或分析的变体。