FEAST: Probing the Stellar Population of the Starburst Dwarf Galaxy NGC 4449 with JWST/NIRCam
Abstract 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.
Authors
- Daniela Calzetti (ORCID: https://orcid.org/0000-0002-5189-8004)
- Thomas S. -Y. Lai (ORCID: https://orcid.org/0000-0001-8490-6632)
- Elena Sabbi (ORCID: https://orcid.org/0000-0003-2954-7643)
- Matteo Correnti (ORCID: https://orcid.org/0000-0001-6464-3257)
- Kelsey E. Johnson (ORCID: https://orcid.org/0000-0001-8348-2671)
- Anne S. M. Buckner (ORCID: https://orcid.org/0000-0002-1832-8229)
- Benjamin Gregg (ORCID: https://orcid.org/0000-0003-4910-8939)
- Matteo Messa (ORCID: https://orcid.org/0000-0003-1427-2456)
- Bruce G. Elmegreen (ORCID: https://orcid.org/0000-0002-1723-6330)
- A. Duarte-Cabral (ORCID: https://orcid.org/0000-0002-5259-4774)
- Göran Östlin (ORCID: https://orcid.org/0000-0002-3005-1349)
- M. Cignoni (ORCID: https://orcid.org/0000-0001-6291-6813)
- Angela Adamo (ORCID: https://orcid.org/0000-0002-8192-8091)
- Kathryn Grasha (ORCID: https://orcid.org/0000-0002-3247-5321)
- Alex Pedrini (ORCID: https://orcid.org/0000-0002-8222-8986)
- J. S. Gallagher (ORCID: https://orcid.org/0000-0001-8608-0408)
- L. J. Smith (ORCID: https://orcid.org/0000-0002-0806-168X)
- Sean T. Linden (ORCID: https://orcid.org/0000-0002-1000-6081)
- M. Tosi (ORCID: https://orcid.org/0000-0002-0986-4759)
- F. Dell’Agli (ORCID: https://orcid.org/0000-0003-2442-6981)
- Elena Sacchi (ORCID: https://orcid.org/0000-0001-5618-0109)
- P. Ventura (ORCID: https://orcid.org/0000-0002-5026-6400)
- Helena Faustino Vieira (ORCID: https://orcid.org/0000-0002-2199-0977)
- Giacomo Bortolini (ORCID: https://orcid.org/0009-0003-6182-8928)
- Drew Lapeer (ORCID: https://orcid.org/0009-0009-5509-4706)
Institutions
- University of Pisa (IT)
- Australian National University (AU)
- California Institute of Technology (US)
- Space Telescope Science Institute (US)
- University of Wisconsin–Madison (US)
- University of Arizona (US)
- Stockholm University (SE)
- University of Massachusetts Amherst (US)
- Leibniz Institute for Astrophysics Potsdam (DE)
- Astronomical Observatory of Rome (IT)
- Agenzia Spaziale Italiana (IT)
- Katonah Museum of Art (US)
- Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna (IT)
- ASTRO-3D (AU)
- Gemini North Observatory (US)
- Université Bourgogne Franche-Comté (FR)
- Gemini South Observatory (CL)
- AlbaNova (SE)
- ARC Centre of Excellence for All-sky Astrophysics (AU)
- Istituto Nazionale di Fisica Nucleare, Sezione di Pisa (IT)
- Infrared Processing and Analysis Center (US)
- Osservatorio di Astrofisica e Scienza dello Spazio
- University of Virginia (US)
- Cardiff University (GB)
- National Institute for Astrophysics (IT)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-08-26
- DOI
- https://doi.org/10.3847/1538-4357/adec74
- Citations
- 4
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 4.62
Funders
- Space Telescope Science Institute