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

Conor Nally*, Olivia C. Jones, Laura Lenkić, Nolan Habel, Alec S. Hirschauer, Margaret Meixner, P. J. Kavanagh, Martha L. Boyer, Annette M. N. Ferguson, B. A. Sargent, Omnarayani Nayak, Tea Temim

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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
Original languageEnglish
Pages (from-to)183-198
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume531
Issue number1
Early online date14 May 2024
DOIs
Publication statusPublished - 1 Jun 2024

Keywords / Materials (for Non-textual outputs)

  • galaxies:dwarf
  • galaxies: irregular
  • Galaxies: individual (NGC 6822)
  • infrared: galaxies
  • infrared: stars
  • stars: AGB and post-AGB

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