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

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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 II λ 4686 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 ) H α component, suggesting the presence of an ionized outflow with a mass loading factor η ∼ 0.2. Finally, we report the robust detection of O I λ 8446 emission (among the firsts at high redshift), which we interpret as originating from Ly β 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.

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