JWST Observations of SN 2023ixf I: Completing the Early Multi-Wavelength Picture with Plateau-phase Spectroscopy

TL;DR

This paper presents early infrared spectroscopy of supernova 2023ixf using JWST, revealing ejecta structures through hydrogen lines and providing insights into molecule and dust formation in the supernova environment.

Contribution

First JWST infrared spectra of SN 2023ixf during the plateau phase, analyzing ejecta structures and dust/molecule formation at early times.

Findings

Ejecta structures inferred from hydrogen line profiles.

No evidence of dust precursor molecules or infrared excess at this epoch.

Ejecta and circumstellar material likely contribute to later molecule and dust detections.

Abstract

We present and analyze panchromatic (0.35--14 $\mu$m) spectroscopy of the Type II supernova 2023ixf, including near- and mid-infrared spectra obtained 33.6 days after explosion during the plateau-phase, with the James Webb Space Telescope (JWST). This is the first in a series of papers examining the evolution of SN 2023ixf with JWST spanning the initial 1000 days after explosion, monitoring the formation and growth of molecules and dust in ejecta and surrounding environment. The JWST infrared spectra are overwhelmingly dominated by H lines, whose profiles reveal ejecta structures, including flat tops, blue notches, and red shoulders, unseen in the optical spectra. We characterize the nature of these structures, concluding that they likely result from a combination of ejecta geometry, viewing angle, and opacity effects. We find no evidence for the formation of dust precursor molecules such as carbon-monoxide (CO), nor do we observe an infrared excess attributable to dust. These observations imply that the detections of molecules and dust in SN 2023ixf at later epochs arise either from freshly synthesized material within the ejecta or circumstellar material at radii not yet heated by the supernova at this epoch.