JWST Observations of SN 2023ixf II: The Panchromatic Evolution Between 250 and 720 Days After the Explosion

TL;DR

This paper presents comprehensive JWST and ground-based observations of supernova 2023ixf from 250 to 720 days post-explosion, revealing spectral, molecular, and dust evolution in the nebular phase.

Contribution

It provides the first detailed panchromatic, late-time dataset of a nearby core-collapse supernova, highlighting spectral features, molecular emission, and dust formation processes.

Findings

Detection of hydrogen emission lines from Balmer to Humphreys series.

Observation of strong CO emission bands weakening over time.

Emergence of infrared excess indicating dust formation.

Abstract

We present the nebular phase spectroscopic and photometric observations of the nearby hydrogen-rich core-collapse supernova (CC-SN) 2023ixf, obtained through our JWST programs. These observations, combined with ground-based optical and near-infrared spectra, cover +252.67 - 719.96 d, creating a comprehensive, panchromatic time-series dataset spanning 0.32 - 30$\mu$m. In this second paper of the series, we focus on identifying key spectral emission features and tracking their evolution through the nebular phase. The JWST data reveal hydrogen emission from the Balmer to Humphreys series, as well as prominent forbidden lines from Ne, Ar, Fe, Co, and Ni. NIRSpec observations display strong emission from the first overtone and fundamental bands of carbon monoxide, which weaken with time as the ejecta cools and dust emission dominates. The spectral energy distribution shows a clear infrared excess emerging by +252.67 d peaking around 10.0$\mu$m, with a secondary bump at 18.0$\mu$m developing by +719.96 d. We suggest that this evolution could arises from multiple warm dust components. In upcoming papers in this series, we will present detailed modeling of the molecular and dust properties. Overall, this dataset significantly advances our understanding of the mid-infrared properties of CC-SNe, providing an unprecedented view of their late-time line, molecule, and dust emission.