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JWST MIRI and NIRCam Unveil Previously Unseen Infrared Stellar Populations in NGC 6822 Published: 9/24/2023 4:29:13 AM Updated: 9/24/2023 4:29:13 AM

Paper abstract: NGC 6822 is a nearby (~490 kpc) non-interacting low-metallicity (0.2Z_\odot) dwarf galaxy which hosts several prominent Hii regions, includingsites of highly embedded active star formation. In this work, we present animaging survey of NGC 6822 conducted with the NIRCam and MIRI instrumentsonboard JWST. We provide a description of the data reduction, sourceextraction, and stellar population identifications from combined near- andmid-infrared (IR) photometry. Our NIRCam observations reach seven magnitudesdeeper than previous JHKs surveys of this galaxy, which were sensitive to justbelow the tip of the red giant branch (TRGB). These JWST observations thusreveal for the first time in the near-IR the red clump stellar population andextend nearly three magnitudes deeper. In the mid-IR, we observe roughly twomagnitudes below the TRGB with the MIRI F770W and F1000W filters. With theseimprovements in sensitivity, we produce a catalogue of ~900,000 pointsources over an area of ~ 6.0 x 4.3 arcmin2. We present several NIRCam andMIRI colour-magnitude diagrams and discuss which colour combinations provideuseful separations of various stellar populations to aid in future JWSTobservation planning. Finally, we find populations of carbon- and oxygen-richasymptotic giant branch stars which will assist in improving our understandingof dust production in low-metallicity, early Universe analogue galaxies.