The Mass-Metallicity Relation of Dwarf Galaxies at Cosmic Noon from JWST Observations
Chevallard, Jacopo; Fan, Xiaohui; Cai, Zheng; Lin, Xiaojing; Li, Mingyu; Wu, Yunjing; Charlot, Stephane; Egami, Eiichi; Sun, Fengwu; Bian, Fuyan; Li, Zihao; Zou, Siwei; Bruzual, Gustavo; Golden-Marx, Emmet; Zhang, Shiwu; Sun, Zechang
China, Chile, United States, France, Mexico, United Kingdom
Abstract
We present a study of the mass-metallicity relation (MZR) of 51 dwarf galaxies (M ⋆ ≈ 106.5-109.5 M ⊙) at z = 2-3 from the A2744 and SMACS J0723-3732 galaxy cluster fields. These dwarf galaxies are identified and confirmed by deep JWST/NIRISS imaging and slitless grism spectroscopic observations. By taking advantage of the superior performance of JWST and the gravitational lensing effect, we extend the previous MZR relation at z = 2-3 to a much lower-mass regime down by ≈2.5 orders of magnitude as compared with previous studies. We find that the MZR has a shallower slope at the low-mass end (M ⋆ < 109 M ⊙), with a slope turnover point of ≈109 M ⊙. This implies that the dominating feedback processes in dwarf galaxies may be different from that in massive galaxies. From z = 3, to z = 2, the metallicity of the dwarf galaxies is enhanced by ≈0.09 dex for a given stellar mass, consistent with the mild evolution found in galaxies with higher mass. Furthermore, we confirm the existence of a fundamental metallicity relation (FMR) between the gas-phase metallicity, stellar mass, and star formation rate in dwarf galaxies at z = 2-3. Our derived FMR, which has no significant redshift evolution, can be used as a benchmark to understand the origin of the anticorrelation between the star formation rate and metallicity of dwarf galaxies in the high-z Universe.