MARTA: The connection between chemical enrichment, feedback, and dust in a Wolf-Rayet galaxy at z ∼ 2

¹ European Southern Observatory, Karl-Schwarzschild Straße 2, D-85748 Garching bei München, Germany
² Università di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone 1, 50019 Sesto Fiorentino, Florence, Italy
³ INAF – Arcetri Astrophysical Observatory, Largo E. Fermi 5, I-50125 Florence, Italy
⁴ Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
⁵ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, DK-2200 Copenhagen, Denmark
⁶ AURA for European Space Agency, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21210, USA
⁷ Department of Physics, University of Arkansas, 226 Physics Building, 825 West Dickson Street, Fayetteville, AR 72701, USA
⁸ Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK
⁹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
¹⁰ Cavendish Laboratory, University of Cambridge, 19 JJ Thomson Avenue, Cambridge CB3 0HE, UK
¹¹ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹² Centro de Astrobiología (CAB), CSIC-INTA, Carretera de Ajalvir km 4 Torrejón de Ardoz, E-28850, Madrid, Spain

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Received: 17 November 2025
Accepted: 17 February 2026

Abstract

We present the analysis of the stellar and interstellar medium (ISM) properties of MARTA-4327, a star-forming galaxy at z = 2.223 observed by means of deep JWST/NIRSpec spectroscopy in both medium- and high-resolution gratings as part of the “Measuring Abundances at high Redshift with the Te Approach” (MARTA) program. We report one of the highest-redshift detections of the Wolf–Rayet (WR) blue and red bumps in a non-lensed system. The broad He IIλ4686 feature is consistent with a young (∼5−6 Myr) burst dominated by WN stars, although both stellar population synthesis models and empirical templates struggle to reproduce nitrogen stellar features at ≈4640 Å. Based on the relative strength of the available optical stellar features, we disfavor the presence of very massive stars (VMS) in this system. Elemental abundance ratios such as Ne/O, N/O, and Ar/O align with observations of local star-forming galaxies (including WR galaxies), suggesting that any impact of the WR population on the chemical enrichment of the ISM is strongly localized. However, the gas-phase Fe/O ratio appears enhanced compared to local galaxies of similar metallicity, which we interpret as evidence for reduced Fe depletion onto dust grains, possibly linked to localized destruction in WR-driven wind environments. In addition, we detect a broad (∼445 km s⁻¹) and blueshifted (∼70 km s⁻¹) Hα component, suggesting the presence of an ionized outflow with a mass loading factor η ∼ 0.2. Finally, we report the robust detection of O Iλ8446 emission (among the firsts at high redshift), which we interpret as originating from Lyβ fluorescence and/or collisional excitation in dense clumps. Overall, MARTA-4327 represents a unique system for studying the role of massive stars in shaping the ISM properties of galaxies at Cosmic Noon.