A JWST Survey of the Supernova Remnant Cassiopeia A

TL;DR

This JWST survey of Cassiopeia A reveals detailed structures of ejecta, dust, and circumstellar material, providing new insights into supernova remnant morphology, shock interactions, and the ISM, with implications for stellar evolution and galaxy enrichment.

Contribution

First JWST imaging and spectroscopy of Cas A that uncovers fine-scale ejecta filaments, dust structures, and light echoes, advancing understanding of supernova remnant complexity.

Findings

Unshocked ejecta filaments exhibit turbulent mixing.

Shocked CSM shows dust-dominated emission with holes from ejecta knots.

Detection of numerous light echoes revealing ISM fine structure.

Abstract

We present initial results from a JWST survey of the youngest Galactic core-collapse supernova remnant Cassiopeia A (Cas A), made up of NIRCam and MIRI imaging mosaics that map emission from the main shell, interior, and surrounding circumstellar/interstellar material (CSM/ISM). We also present four exploratory positions of MIRI/MRS IFU spectroscopy that sample ejecta, CSM, and associated dust from representative shocked and unshocked regions. Surprising discoveries include: 1) a web-like network of unshocked ejecta filaments resolved to 0.01 pc scales exhibiting an overall morphology consistent with turbulent mixing of cool, low-entropy matter from the progenitor's oxygen layer with hot, high-entropy matter heated by neutrino interactions and radioactivity, 2) a thick sheet of dust-dominated emission from shocked CSM seen in projection toward the remnant's interior pockmarked with small (approximately one arcsecond) round holes formed by knots of high-velocity ejecta that have pierced through the CSM and driven expanding tangential shocks, 3) dozens of light echoes with angular sizes between 0.1 arcsecond to 1 arcminute reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission from the neutron star in Cas A's center and tightly constrain scenarios involving a possible fallback disk. These JWST survey data and initial findings help address unresolved questions about massive star explosions that have broad implications for the formation and evolution of stellar populations, the metal and dust enrichment of galaxies, and the origin of compact remnant objects.