Resolving the Dusty Star-forming Galaxy GN20 at z = 4.055 with NOEMA and JWST: A Similar Distribution of Stars, Gas, and Dust Despite Distinct Apparent Profiles
Year: 2025
Type: article
Abstract: We present high-resolution (0 . ″ 13–0 . ″ 23) NOEMA observations of the dust continuum emission at 1.1 mm (rest frame 220 μ m) and JWST/NIRCam and MIRI imaging of the z = 4.055 starburst galaxy GN20. The sensitive NOEMA imaging at 1.6 kpc resolution reveals extended dust emission, ≈14 kpc in diameter ( r e ≈ 2.5 kpc, b / a = 0.5), which is centrally asymmetric and clumpy. The dust emission is as extended as the stellar emission and molecular gas traced by 12 CO(2–1), with a common center, and is brightest in the strongly obscured nuclear part of the galaxy. Approximately one-third of the total dust emission emerges from the nucleus and the most prominent clump to the south, with (only) 60% from the central 3.5 × 1.5 kpc (0 . ″ 5–0 . ″ 2), implying that the starburst is very extended. The combined JWST and NOEMA morphology suggests GN20 experienced a recent interaction or merger, likely invigorating the starburst. The radial surface brightness profiles of the molecular gas and near-IR stellar emission are similar, while, in contrast, the dust emission appears significantly more concentrated. Through self-consistent radiative-transfer modeling of the integrated and resolved 12 CO and dust emission, we derive M mol = 2 . 9 − 0.3 + 0.4 × 1 0 11 f M ⊙ , with α CO = 2 . 8 − 0.3 + 0.5 . We find the extended dust implies a lower global dust optical depth than previously reported but a high dust mass of M dust = 5 . 7 − 0.6 + 0.8 × 1 0 9 M ⊙ and gas-to-dust ratio of ≈50. Furthermore, we show that the distinct apparent radial profiles of the gas and dust can be explained purely by radiative-transfer effects (differences in the radial optical depths and temperatures), and that the observations are consistent with the gas
Source: The Astrophysical Journal
Institutions: Leiden University, Leiden Observatory, National Radio Astronomy Observatory, Max Planck Institute for Astronomy, Max Planck Society, Max Planck Institute for Radio Astronomy, Centro de Astrobiología, Stockholm University, AlbaNova, Space Telescope Science Institute, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Astrophysique, Instrumentation et Modélisation, Sorbonne Paris Cité, University of Copenhagen, DTU Space, Technical University of Denmark, University of Geneva
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: Space Telescope Science Institute, Swedish National Space Agency, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Ministerio de Ciencia e Innovación, European Regional Development Fund, Agencia Estatal de Investigación
OpenAlex ID: W7116874018