JWST Observations of SN 2024ggi I: Interpretation and Model Comparison of the Type II Supernova 2024ggi at 55 days Past Explosion

TL;DR

This paper presents comprehensive panchromatic observations of the Type II supernova 2024ggi at 55 days post-explosion, using JWST and ground-based spectra, and compares these with models and other supernovae to understand ejecta properties.

Contribution

It provides the first detailed panchromatic dataset of SN 2024ggi at this epoch and compares it with models and other supernovae, highlighting spectral features and model limitations.

Findings

Spectral features dominated by HI emission

No MIR excess or dust detected at 55 days

Model reproduces continuum but has shortcomings in density profile

Abstract

We present panchromatic 0.4-21 microns observations of the nearby (about 7.2 Mpc) Type II supernova 2024ggi, obtained during the plateau phase at about 55 d past explosion. Our dataset includes JWST spectra spanning 1.7-14 microns, MIR imaging at 7.7 and 21 microns, and near-simultaneous ground-based optical and NIR spectra covering 0.32-1.8 microns. The NIR and MIR spectral features of SN 2024ggi are dominated by HI emission. We present line IDs and a toy PHOENIX/1D model that reproduces the observations well, especially the continuum redward of 0.9 microns We compare SN 2024ggi to SN 2022acko and SN 2023ixf, two other Type II supernovae that were also observed by JWST, and highlight key similarities and differences in their spectral features. No evidence for a MIR excess or dust is found at these epochs, with the model matching the observed flux out to 21 microns. We discuss the model's shortcomings, focusing on the density profile, which suppresses line blanketing and produces features in the optical that are too narrow. Our results show the power of panchromatic studies in both exploring the nature of the SN ejecta and constraining detailed models of SNe.