A JWST Survey of the Supernova Remnant Cassiopeia A

Abstract

We present initial results from a James Webb Space Telescope (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 Medium Resolution Spectrograph integral field unit spectroscopy that sample ejecta, CSM, and associated dust from representative shocked and unshocked regions. Surprising discoveries include (1) a weblike 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 (∼1″) round holes formed by ≲0.″1 knots of high-velocity ejecta that have pierced through the CSM and driven expanding tangential shocks; and (3) dozens of light echoes with angular sizes between ∼0.″1 and 1′ reflecting previously unseen fine-scale structure in the ISM. NIRCam observations place new upper limits on infrared emission (≲20 nJy at 3 μm) 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.

Shockingly Bright Warm Carbon Monoxide Molecular Features in the Supernova Remnant Cassiopeia A Revealed by JWST

“…These observations were obtained as part of a Cycle 1 survey program on Cas A (Prog. ID of 1947), described in Milisavljevic et al (2024). The NIRCam images were taken on 2022 December 5-6, using the F356W (3.140-3.980 μm) and F444W (3.880-4.986 μm) filters.…”

“…Each NIRSpec-IFU position covers a region 3 7 × 4″ in size with 0 1 pixels. Four IFU positions were observed for the program, as described in Milisavljevic et al (2024). two regions are reported by I.…”

“…two regions are reported by I. De Looze (2024, in preparation) and Milisavljevic et al (2024). We extracted the JWST NIRSpec-IFU spectra from each pixel, and the total ∼1368 spectra are from 36 × 38 detector pixels.…”

“…The effective integration and total exposure times are 145 and 583 s for the N field and 218 and 875 s for the S field, respectively. More details of the JWST observations of Cas A are described in Milisavljevic et al (2024).…”

Supernova Ejecta with Crystalline Silicate Dust in the Supernova Remnant MSH 15–52

“…Hence, IRAS 15099-5856 is likely "pristine" SN ejecta material, not processed by a reverse shock. Such pristine dusty ejecta has been found in Cas A as well, although the heating source in this case is the radiative heating from reverse shock (Laming & Temim 2020;Milisavljevic et al 2024). Koo et al (2011) investigated the central compact source (IRS1) of IRAS 15099-5856 with the AKARI MIR imaging observations and the Spitzer InfraRed Spectrograph (IRS) spectroscopy.…”