JWST MIRI and NIRCam Unveil Previously Unseen Infrared Stellar Populations in NGC 6822
arxiv(2023)
摘要
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
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