Duration and properties of the embedded phase of star formation in 37 nearby galaxies from PHANGS-JWST

¹ Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik Albert-Ueberle-Str. 2 69120 Heidelberg, Germany
² Cosmic Origins Of Life (COOL) Research DAO, https://coolresearch.io, Germany
³ Kavli Institute for Particle Astrophysics & Cosmology, Stanford University CA 94305, USA
⁴ INAF – Osservatorio Astrofisico di Arcetri Largo E. Fermi 5 I-50125 Florence, Italy
⁵ European Southern Observatory Karl-Schwarzschild Straße 2 D-85748 Garching bei München, Germany
⁶ Department of Physics, University of Arkansas, 226 Physics Building 825 West Dickson Street Fayetteville AR 72701, USA
⁷ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange 06000 Nice, France
⁸ Department of Astronomy, The Ohio State University 140 West 18th Avenue Columbus OH 43210, USA
⁹ Department of Physics and Astronomy, University of Wyoming Laramie WY 82071, USA
¹⁰ Department of Astronomy, University of Cape Town Rondebosch 7701 Cape Town, South Africa
¹¹ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg Mönchhofstraße 12-14 D-69120 Heidelberg, Germany
¹² Research School of Astronomy and Astrophysics, Australian National University Canberra ACT 2611, Australia
¹³ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
¹⁴ Dept. of Physics, University of Alberta, 4-183 CCIS Edmonton Alberta T6G 2E1, Canada
¹⁵ Gemini Observatory/NSF NOIRLab 950 N Cherry Avenue Tucson AZ 85719, USA
¹⁶ Department of Astronomy & Astrophysics, University of California, San Diego 9500 Gilman Dr. La Jolla CA 92093, USA
¹⁷ Center for Cosmology and Astroparticle Physics 191 West Woodruff Avenue Columbus OH 43210, USA
¹⁸ Instituto de Astronomía, Universidad Nacional Autónoma de México Ap. 70-264 04510 CDMX, Mexico
¹⁹ Max-Planck-Institut für Astronomie Königstuhl 17 D-69117 Heidelberg, Germany
²⁰ Department of Physics, Tamkang University, No.151, Yingzhuan Road Tamsui District New Taipei City 251301, Taiwan
²¹ Department of Physics and Astronomy, The Johns Hopkins University Baltimore MD 21218, USA
²² Department of Astrophysical Sciences, Princeton University 4 Ivy Lane Princeton NJ 08544, USA
²³ Whitman College 345 Boyer Avenue Walla Walla WA 99362, USA
²⁴ Space Telescope Science Institute 3700 San Martin Drive Baltimore MD 21218, USA
²⁵ Sub-department of Astrophysics, Department of Physics, University of Oxford Keble Road Oxford OX1 3RH, UK

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Received: 1 July 2025
Accepted: 3 December 2025

Abstract

Light reprocessed by dust grains emitting in the infrared enables the study of the physics at play in dusty embedded regions, where ultraviolet and optical wavelengths are attenuated. Infrared telescopes such as JWST have made it possible to study the earliest feedback phases, when stars are shielded by cocoons of gas and dust. Comprehending this phase is crucial for unravelling the effects of feedback from young stars that leads to their emergence and the dispersal of their host molecular clouds. Here we show that the transition from the embedded to the exposed phase of star formation is short (< 4 Myr) and sometimes almost absent (< 1 Myr) across a sample of 37 nearby star-forming galaxies covering a wide range of morphologies, from massive barred spirals to irregular dwarfs. The short duration of the dust-clearing timescales suggests a predominant role of pre-supernova feedback mechanisms in revealing newborn stars, confirming previous results on smaller samples and allowing, for the first time, a statistical analysis of their dependencies. We find that the timescales associated with mid-infrared emission at 21 μm, tracing a dust-embedded feedback phase, are controlled by a complex interplay between giant molecular cloud properties (masses and velocity dispersions) and galaxy morphology. We report relatively longer durations of the embedded phase of star formation in barred spiral galaxies, while this phase is significantly reduced in low-mass irregular dwarf galaxies. We discuss tentative trends with gas-phase metallicity, which may favor faster cloud dispersal at low metallicities.