JWST View of the Supernebula in NGC 5253. I. Overview and Continuum Features

We present 5–28 μ m imaging spectroscopy of the “supernebula” in the dwarf galaxy NGC 5253 made with the JWST/MIRI/Medium Resolution Spectrometer integral field spectrometer. NGC 5253 hosts a luminous ( L ∼ 10 9 L ⊙ ) H II region, powered by a giant young star cluster, a possible local analog to super star cluster formation at Cosmic Dawn and Noon. In this paper, the first in a series about the mid-infrared (MIR) line and continuum emission in the center of NGC 5253, we present an overview and continuum spectra. The MIR images reveal four continuum sources that we identify as hot dust emission from luminous H II regions. The dominant source is the parsec-scale supernebula core seen at radio wavelengths. We find that the MIR-to-radio continuum flux ratio is identical to that of Galactic H II regions. The 9.7 μ m silicate feature is present and strongest in absorption toward the supernebula. Polycyclic aromatic hydrocarbon (PAH) features at 6.2, 6.8, 7.7, 8.6, and 11.2 μ m are detected across the region, although weakly, particularly in the supernebula. Unusual PAH line profiles are seen, including a broad 6 μ m feature, likely in part aliphatic, from the extended starburst region and strong 11.0 μ m emission from the supernebula. These observations suggest dust processing by intense radiation fields and possible dust production and dispersal by Wolf–Rayet stars within the region.