The Near Infrared Spectral Energy Distribution of Young Star Clusters in the FEAST Galaxies: Missing Ingredients at 1–5 μm
Year: 2025
Type: article
Abstract: We present a combined Hubble Space Telescope (HST) and JWST 0.2–to–5 μm analysis of the spectral energy distributions (SED) of emerging young star clusters (eYSCs) in four nearby galaxies from the Feedback in Emerging Extrgalactic Star Clusters survey: M51, M83, NGC 628, and NGC 4449. These clusters, selected for their bright Paα and 3.3 μm polycyclic aromatic hydrocarbon emission, are still associated with their natal gas cloud and have been largely missed in previous HST optical campaigns. We modeled their SEDs using the CIGALE fitting code and identified (i) a systematic flux excess at 1.5–2.5 μm that is not accounted for by current stellar population models and (ii) the preference for a set of dust model parameters that is not aligned with expectations from self-consistent analyses of star-forming regions, suggesting model shortcomings also in the 3–5 μm. The near-infrared excess is most prominent in low-mass (≤3000 M ⊙) and young (≤6 Myr) clusters. Additionally, we see that the SED fitting analysis wrongly assigns ages ≥6 Myr to a fraction of strong Paα emitters with equivalent widths suggestive of significantly younger ages. A parallel analysis with the slug code suggests that stochastic initial mass function (IMF) sampling of pre-main-sequence stars combined with extinction might partially reduce the gap. We conclude that the inclusion of young stellar object SEDs, along with more realistic sampling of the cluster IMF, might be needed to fully account for the stellar population and dust properties of eYSCs.
Source: The Astrophysical Journal
Authors: Alex Pedrini, Angela Adamo, Arjan Bik, Daniela Calzetti, Sean T. Linden, Benjamin Gregg, Varun Bajaj, Jenna E. Ryon, Anne S. M. Buckner, Giacomo Bortolini, Michele Cignoni, Matteo Correnti, Ana Duarte-Cabral, Bruce G. Elmegreen, Helena Faustino Vieira, John S. Gallagher, Kathryn Grasha, Kelsey E. Johnson, Mark R. Krumholz, Drew Lapeer, Thomas S.-Y. Lai, Matteo Messa, Göran Östlin, Linn Roos, Linda J. Smith, Monica Tosi
Institutions: Stockholm University, AlbaNova, University of Massachusetts Amherst, University of Arizona, Space Telescope Science Institute, Cardiff University, University of Pisa, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Osservatorio di Astrofisica e Scienza dello Spazio, National Institute for Astrophysics, Astronomical Observatory of Rome, Agenzia Spaziale Italiana, University of Wisconsin–Madison, Australian National University, ASTRO-3D, ARC Centre of Excellence for All-sky Astrophysics, University of Virginia, California Institute of Technology, Infrared Processing and Analysis Center, Uppsala University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Award: G4665460038
OpenAlex ID: W4414925003