[论文解读] SN H0pe: The First Measurement of $H_0$ from a Multiply-Imaged Type Ia Supernova, Discovered by JWST

Massimo Pascale, Brenda Frye+22 more|arXiv (Cornell University)|Mar 27, 2024

Gamma-ray bursts and supernovae被引用 9

一句话总结

本论文利用 JWST 发现的三重成像型 Ia 超新星（SN H0pe）来测量Hubble常数 H0，结合光度测量、光谱观测以及七个独立的透镜模型，在放大因子约束下推断 H0。

ABSTRACT

The first James Webb Space Telescope ({\it JWST}) Near InfraRed Camera (NIRCam) imaging in the field of the galaxy cluster PLCK G165.7+67.0 ($z=0.35$) uncovered a Type Ia supernova (SN Ia) at $z=1.78$, called ``SN H0pe." Three different images of this one SN were detected as a result of strong gravitational lensing, each one traversing a different path in spacetime, thereby inducing a relative delay in the arrival of each image. Follow-up {\it JWST} observations of all three SN images enabled photometric and rare spectroscopic measurements of the two relative time delays. Following strict blinding protocols which oversaw a live unblinding and regulated post-unblinding changes, these two measured time delays were compared to the predictions of seven independently constructed cluster lens models to measure a value for the Hubble constant, $H_0=71.8^{+9.2}_{-8.1}$ km s$^{-1}$ Mpc$^{-1}$. The range of admissible $H_0$ values predicted across the lens models limits further precision, reflecting the well-known degeneracies between lens model constraints and time delays. It has long been theorized that a way forward is to leverage a standard candle, but this has not been realized until now. For the first time, the lens models are evaluated by their agreement with the SN absolute magnifications, breaking degeneracies and producing our best estimate, $H_0=75.7^{+8.1}_{-5.5}$ km s$^{-1}$ Mpc$^{-1}$. This is the first precision measurement of $H_0$ from a multiply-imaged SN Ia and only the second from any multiply-imaged SN.

研究动机与目标

• 在强引力透镜作用下，使用 SN Ia 作为标准烛光来激励和测试时间延迟宇宙学。
• 利用来自 SN Ia 的绝对放大来破坏簇透镜中的质量模型退化。
• 在盲法下，将光度与光谱观测与多种透镜模型相结合以推断 H0。
• 证明 SN Ia 标准烛光在中等红移下也能给出对 H0 的精确约束。

提出的方法

• 用透镜预测的时延再乘以 H0 通过 DDelta_t（Eq. 3）来重新缩放以建模时间延迟。
• 在相同输入约束下构建七个独立的簇透镜模型（参数化、非参数化和半参数化）。
• 在贝叶斯框架下结合时间延迟与放大倍数推断 H0（Eqs. 4–7）。
• 将绝对放大倍数作为额外观测量量纳入，以破除透镜模型中的退化。
• 采用盲法分析以防止偏见，去盲细节在附录中讨论。

Figure 1: JWST /NIRCam color image in the central region of G165. Insets show closeup of the boxed region depicting the three images of the host galaxy Arc 2 prior to SN H0pe in HST WFC3/IR F160W imaging from 2016 (lower left) and during its appearances in JWST /NIRCam F150W imaging from 2023 (upper

实验结果

研究问题

• RQ1 在星系团中形成多重像的 SN Ia 是否能够给出具有竞争力的 H0 测量？
• RQ2 SN像的绝对放大是否有助于打破透镜模型的退化，从而收窄 H0 的约束？
• RQ3 光度与光谱时间延迟如何比较并结合来约束 H0？
• RQ4 使用多样化透镜模型对推断的 H0 及其不确定性有什么影响？

主要发现

• 仅通过时间延迟在各模型中的 H0 推断为 71.8 +9.8/-7.6 km s-1 Mpc-1（在去盲前的盲法分析）。
• 将 SN 绝对放大纳入后，H0 收敛为 75.4 +8.1/-5.5 km s-1 Mpc-1。
• 光度与光谱分析提供一致的时间延迟测量，使得对 H0 的联合推断成为可能。
• 七种透镜模型，涵盖参数化和非参数化方法，导致预测的时间延迟和放大存在差异，揭示模型系统偏差。
• 这项工作首次给出来自多重像 SN Ia 的精确 H0 测量，并支持与早期宇宙 H0 值的紧张不一致。

Figure 2: High signal-to-noise NIRSpec spectrum of SN H0pe. The G140M (green) and G235M (blue) grating spectra are shown. Some prominent line features are identified, such as the [Si II] line blueshifted to rest-frame $\sim 6150$ Å that is a requiste line feature of a Type Ia supernova. A couple of