FEAST: JWST/NIRCam view of the resolved stellar populations of the interacting dwarf galaxies NGC 4485 and NGC 4490

Bortolini, Giacomo, Correnti, Matteo, Adamo, Angela, Cignoni, Michele, Sacchi, Elena, Tosi, Monica, Östlin, Göran, Kapodistrias, Anastasios, Bik, Arjan, Calzetti, Daniela, Duarte-Cabral, Ana ORCID: https://orcid.org/0000-0002-5259-4774, Dell’Agli, Flavia, Gallagher, John S., Gregg, Benjamin, Grasha, Kathryn, Lai, Thomas S.-Y., Lapeer, Drew, Linden, Sean T., Messa, Matteo, Pedrini, Alex, Sabbi, Elena, Smith, Linda J., Faustino Vieira, Helena, Cannon, John M., Puertas, Salvador Duarte and Robert, Carmelle 2025. FEAST: JWST/NIRCam view of the resolved stellar populations of the interacting dwarf galaxies NGC 4485 and NGC 4490. The Astrophysical Journal 991 , 212. 10.3847/1538-4357/adfccc

PDF - Published Version Available under License Creative Commons Attribution. Download (49MB)

Abstract

We present new JWST/NIRCam observations of the interacting dwarf galaxy system NGC 4485–NGC 4490 (aka Arp 269), obtained as part of the Cycle 1 Feedback in Emerging Extragalactic Star Clusters (FEAST) program. NGC 4485 and NGC 4490 form the closest known pair of interacting late-type dwarf galaxies (at ∼7.4 Mpc), excluding the Magellanic Clouds. Near-infrared color–magnitude diagrams (CMDs) reveal a wide range of stellar populations in both galaxies, including young (≲200 Myr) upper main-sequence stars, core helium-burning stars, and oxygen-rich asymptotic giant branch (AGB) stars. We also identify intermediate-age (∼200 Myr–1 Gyr) carbon-rich AGB stars and a well-populated old (≳1 Gyr) red giant branch. The CMDs show two distinct bursts of star formation beginning ∼30 and ∼200 Myr ago, the latter consistent with the most recent pericenter passage predicted by N-body simulations. The spatial distribution of stars reveals a tidal bridge extending from NGC 4485 and connecting to the disk of NGC 4490. Compact star-forming regions are seen along NGC 4490’s spiral arms, possibly originating from its infrared nucleus. A significant metallicity gradient is observed in the young stellar populations forming the bridge. These findings suggest that during the last pericenter passage, gas was stripped from NGC 4485 via tidal forces or ram pressure, accreted by NGC 4490, and mixed with in situ material, fueling ongoing star formation. This system provides a unique nearby laboratory for studying how tidal interactions shape the star formation and chemical enrichment history of dwarf galaxies.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Type: cc-by
Publisher:	American Astronomical Society
ISSN:	0004-637X
Date of First Compliant Deposit:	7 October 2025
Date of Acceptance:	17 August 2025
Last Modified:	07 Oct 2025 10:45
URI:	https://orca.cardiff.ac.uk/id/eprint/181519

Actions (repository staff only)

Edit Item