Gas-Phase Metallicity and Nitrogen Abundances in Low-Mass Galaxies Down to M 10 5.7,M at z 4.5 -- 10.1 from JWST Lensing Cluster Surveys

arXiv:2607.15515 · astro-ph.GA · Submitted 2026-07-17 · Read on arXiv

Hiroya Umeda, Masami Ouchi, Kimihiko Nakajima, Kuria Watanabe, Yuichi Harikane, Yuki Isobe, Moka Nishigaki, Ono Yoshiaki, Hidenobu Yajima, Yi Xu

astro-ph.GA

Submitted: 2026-07-17

Comments: 35 pages, submitted to the Astrophysical Journal

Project page: https://dawn-cph.github.io/dja

License: http://creativecommons.org/licenses/by/4.0/

The gist: We analyze 405 deep JWST/NIRSpec spectra of star-forming galaxies at z=4.5 -- 10.1 from DREAMS and other lensing-cluster surveys to study chemical enrichment in intrinsically faint, low-mass galaxies.

Terminology

Abstract

We analyze 405 deep JWST/NIRSpec spectra of star-forming galaxies at z=4.5 -- 10.1 from DREAMS and other lensing-cluster surveys to study chemical enrichment in intrinsically faint, low-mass galaxies. The sample covers M UV-12 to-22 and reaches M 10 5.7,M, with 50% of the sources at M UV>-17.5 magnified by mu>3. From individual spectra and mass-binned stacks, we derive the gas-phase metallicity together with nitrogen and carbon abundances using the rest-frame UV and optical lines. In the M 10 7.7,M stack, N/O from N, iv], lambda lambda,1483,1486 exceeds that from [N, ii], lambda6583 by 1.4 dex. The UV--optical difference could indicate a localized, highly ionized N-rich component whose high N/O and subsolar C/O resemble nitrogen-rich globular-cluster populations with M 10 6,M. The combination of these abundance patterns and a He, ii, 4686/H beta ratio of 0.03, well above BPASS predictions, suggests that WR stars may contribute both prompt CNO-cycle enrichment and hard ionizing radiation, with the inferred WR population potentially supplying enough nitrogen to account for the excess on globular-cluster scales.

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