JWST MIRI and NIRCam Unveil Previously Unseen Infrared Stellar Populations in NGC 6822

TL;DR

This study uses JWST's NIRCam and MIRI instruments to uncover previously unseen infrared stellar populations in NGC 6822, revealing detailed features of its low-metallicity galaxy's stars and aiding future research.

Contribution

First infrared detection of the red clump and deep stellar populations in NGC 6822 using JWST, expanding understanding of its stellar content and aiding future observations.

Findings

Revealed red clump population in NGC 6822 for the first time in near-IR.

Extended detection of stellar populations nearly three magnitudes deeper than previous surveys.

Identified carbon- and oxygen-rich asymptotic giant branch stars relevant for dust production studies.

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 of highly embedded active star formation. In this work, we present an imaging survey of NGC 6822 conducted with the NIRCam and MIRI instruments onboard JWST. We describe the data reduction, source extraction, and stellar population identifications from combined near- and mid-infrared (IR) photometry. Our NIRCam observations reach seven magnitudes deeper than previous JHKs surveys of this 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-IR the red clump stellar population and extend nearly three magnitudes deeper. In the mid-IR, we observe roughly two magnitudes below the TRGB with the MIRI F770W and F1000W filters. With these improvements in sensitivity, we produce a catalogue of ~900,000 point sources over an area of ~ 6.0 x 4.3 arcmin2. We present several NIRCam and MIRI colour-magnitude diagrams and discuss which colour combinations provide useful separations of various stellar populations to aid in future JWST observation planning. Finally, we find populations of carbon- and oxygen-rich asymptotic giant branch stars which will assist in improving our understanding of dust production in low-metallicity, early Universe analogue galaxies