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Arxiv: JWST MIRI and NIRCam Unveil Previously Unseen Infrared Stellar Populations in NGC 6822 Published: 9/24/2023 4:29:13 AM Updated: 4/29/2024 6:16:11 PM

Paper abstract: NGC 6822 is a nearby (~490 kpc) non-interacting low-metallicity (0.2 Zsolar)dwarf galaxy which hosts several prominent H ii regions, including sites ofhighly embedded active star formation. In this work, we present an imagingsurvey of NGC 6822 conducted with the NIRCam and MIRI instruments onboard JWST.We describe the data reduction, source extraction, and stellar populationidentifications from combined near- and mid-infrared (IR) photometry. OurNIRCam observations reach seven magnitudes deeper than previous JHKs surveys ofthis galaxy, which were sensitive to just below the tip of the red giant branch(TRGB). These JWST observations thus reveal for the first time in the near-IRthe red clump stellar population and extend nearly three magnitudes deeper. Inthe mid-IR, we observe roughly two magnitudes below the TRGB with the MIRIF770W and F1000W filters. With these improvements in sensitivity, we produce acatalogue of ~900,000 point sources over an area of ~ 6.0 x 4.3 arcmin2. Wepresent several NIRCam and MIRI colour-magnitude diagrams and discuss whichcolour combinations provide useful separations of various stellar populationsto aid in future JWST observation planning. Finally, we find populations ofcarbon- and oxygen-rich asymptotic giant branch stars which will assist inimproving our understanding of dust production in low-metallicity, earlyUniverse analogue galaxies