LensWatch. II. 利用HST模板观测改进对强透镜Ia型超新星2022qmx（“SN Zwicky”）的测光与时延约束
LensWatch. II. Improved Photometry and Time-delay Constraints on the Strongly Lensed Type Ia Supernova 2022qmx ("SN Zwicky") with HST Template Observations
AI总结：
本文利用HST模板观测对强透镜Ia型超新星SN Zwicky进行改进测光，获得更精确的时延与放大率约束，并发现像A、C及可能D中的微透镜效应可解释其异常放大率。
摘要：
强透镜超新星（SNe）是一类罕见的暂现源，能够提供与其他天文事件方法互补的紧密宇宙学约束。我们对一颗近期发现的强透镜超新星——位于z = 0.3544的四重成像Ia型超新星SN 2022qmx（又称“SN Zwicky”）进行了后续研究。我们测量了SN Zwicky更新后的模板扣除测光数据，并推导出改进的时延和放大率。这是可能的，因为超新星是暂现源，在达到峰值亮度后会逐渐变暗。具体而言，我们在三个哈勃空间望远镜WFC3/UVIS波段（F475W、F625W、F814W）和一个WFC3/IR波段（F160W）中测量了SN Zwicky全部四个像的点扩散函数（PSF）测光，模板图像在超新星像出现的历元之后约11个月拍摄。我们发现透镜模型预测的时延（≲1天）与利用HST颜色测量的时延（≲2天）在2σ范围内一致，其中包括可能由透镜星系中恒星引起的色差微透镜效应所带来的不确定性。Ia型超新星的可标准化特性使我们能够估计四个像的绝对放大率，其中像A和像C的放大率相对于透镜模型预测分别高出约6σ和3σ，证实了之前的工作。我们表明毫透镜或差分尘埃消光无法解释这些差异，并发现证据表明像A、C以及可能D中存在微透镜效应，这可能是导致异常放大率的原因之一。
英文摘要：
Strongly lensed supernovae (SNe) are a rare class of transient that can offer tight cosmological constraints that are complementary to methods from other astronomical events. We present a follow-up study of one recently-discovered strongly lensed SN, the quadruply-imaged Type Ia SN 2022qmx (aka, "SN Zwicky") at z = 0.3544. We measure updated, template-subtracted photometry for SN Zwicky and derive improved time delays and magnifications. This is possible because SNe are transient, fading away after reaching their peak brightness. Specifically, we measure point spread function (PSF) photometry for all four images of SN Zwicky in three Hubble Space Telescope WFC3/UVIS passbands (F475W, F625W, F814W) and one WFC3/IR passband (F160W), with template images taken $\sim 11$ months after the epoch in which the SN images appear. We find consistency to within $2σ$ between lens model predicted time delays ($\lesssim1$ day), and measured time delays with HST colors ($\lesssim2$ days), including the uncertainty from chromatic microlensing that may arise from stars in the lensing galaxy. The standardizable nature of SNe Ia allows us to estimate absolute magnifications for the four images, with images A and C being elevated in magnification compared to lens model predictions by about $6σ$ and $3σ$ respectively, confirming previous work. We show that millilensing or differential dust extinction is unable to explain these discrepancies and find evidence for the existence of microlensing in images A, C, and potentially D, that may contribute to the anomalous magnification.
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