James Webb Space Telescope Feed Post

JWST NIRCam Observations of SN 1987A: Spitzer Comparison and Spectral Decomposition

Comparison of IRAC and NIRCam images at comparable wavelengths provides a qualitative indication that the high-resolution mapping and deconvolution of the IRAC data (Arendt et al. 2020) had revealed hints of the true structure of the SNR emission, and that there have been no major changes between the Spitzer and JWST eras. Abstract: JWST Near Infrared Camera (NIRCam) observations at 1.5–4.5 µm have provided broadband and narrowband imaging of the evolving remnant of SN 1987A with unparalleled sensitivity and spatial resolution. Comparing with previous marginally spatially resolved Spitzer Infrared Array Camera (IRAC) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (ER), and the current brightness at 3.6 and 4.5 µm was accurately predicted by extrapolation of the declining brightness tracked by IRAC. Despite the regular light curve, the NIRCam observations clearly reveal that much of this emission is from a newly developing outer portion of the ER. Spots in the outer ER tend to lie at position angles in between the well-known ER hotspots. We show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. This spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively.