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FEAST: Probing the Stellar Population of the Starburst Dwarf Galaxy NGC 4449 with JWST/NIRCam
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).ORCID iD: 0009-0003-6182-8928
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).ORCID iD: 0000-0002-8192-8091
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Number of Authors: 252025 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 990, no 1, article id 72Article in journal (Refereed) Published
Abstract [en]

We present new JWST/NIRCam observations of the starburst irregular galaxy NGC 4449, obtained in Cycle 1 as part of the Feedback in Emerging extrAgalactic Star clusTers program, which we use to investigate its resolved stellar populations and their spatial distributions. NGC 4449 near-IR color-magnitude diagrams reveal a broad range of stellar populations, spanning different evolutionary phases, from young main sequence stars, to old red giant branch stars and asymptotic giant branch (AGB) stars. The analysis of their spatial distributions shows that younger (≤10 Myr) populations form an S-shaped distribution aligned with the galaxy’s north-south axis, while stars aged 10-60 Myr show shifting concentrations from the north to the south, consistent with the possibility that external interactions or tidal effects may have triggered star formation in spatially distinct bursts. Clusters of comparable ages generally follow these distributions, suggesting that cluster and field stars form at the same pace in each galaxy region. Thanks to the unprecedented high-spatial resolution and sensitivity of the JWST data, we recover a clear gap between oxygen-rich and the carbon star branch of the AGB population, as well as the presence of a massive AGB star “finger.” The analysis of these stars can provide constraints on AGB evolution models and dust production in this galaxy. These results confirm NGC 4449's status as a compelling example of a local dwarf starburst galaxy undergoing complex and possibly externally driven star formation and underscore the power of JWST in probing the full lifecycle of stars in nearby starburst systems.

Place, publisher, year, edition, pages
2025. Vol. 990, no 1, article id 72
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Astronomy, Astrophysics and Cosmology
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URN: urn:nbn:se:su:diva-246679DOI: 10.3847/1538-4357/adec74ISI: 001556896800001Scopus ID: 2-s2.0-105014179485OAI: oai:DiVA.org:su-246679DiVA, id: diva2:1996439
Available from: 2025-09-09 Created: 2025-09-09 Last updated: 2025-09-09Bibliographically approved

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Bortolini, GiacomoAdamo, AngelaPedrini, AlexÖstlin, Göran

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