Asymptotic giant branch stars in NGC 6822: Probes of star formation history

Gallart, C.; Aparicio, A.; Chiosi, C.; Bertelli, G.; Vilchez, J. M.
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Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 425, no. 1, p. L9-L12

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About 500 asymptotic giant branch (AGB) stars have been resolved and photometrically measured in the Local Group (LG) dwarf irregular galaxy NGC 6822. They draw an AGB well shaped, densely populated, and extending to very red colors. It is the first time that this kind of AGB has been clearly detected. Using recent stellar evolutionary models and isochrones, we discuss the stellar population of the galaxy, showing, in particular, how the structure of the AGB can be used as an observable to trace the intermediate-age and old star formation history of the galaxy. The powerful telescopes and detectors currently available offer the opportunity of detecting this structure in other nearby galaxies. This opens new paths for the study of the intermediate-age and old populations of the LG.