James Webb Space Telescope Feed Post

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

NIRCam images of SN 1987A reprojected onto a common (a, d) coordinate grid. The top row contains the broadband images. The middle row shows narrowband images that are respectively centered on lines for: [Fe ii]+[Si i], H2, H2 (also), and H i. The images are logarithmically scaled from 0.32 to 32 MJy sr-1 (after adding an offset of 0.5 MJy sr-1) and show a field of view of 5' × 5'. North is up and east is to the left in all images in this paper. The red dots in the lower left corner of each panel indicate the FWHM size of the PSF. The relative brightness variations between the inner ejecta, the hotspots of the ER, and the emission beyond the ER hotspots indicate a variety of emission mechanisms at work. The bottom row emphasizes the line emission in each of the narrow bands by subtracting scaled versions of the wideband emission. 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.