Revisiting the mass metallicity relation and the fundamental metallicity relation of dwarf galaxies at cosmic noon with NIRISS

TL;DR

This study uses JWST/NIRISS data to analyze the mass-metallicity relation of dwarf galaxies at high redshift, confirming its robustness and exploring the fundamental metallicity relation with no clear SFR dependence.

Contribution

It provides the largest sample of high-redshift dwarf galaxies with NIRISS, confirming the universality of the MZR and testing the FMR's existence at cosmic noon.

Findings

The MZR slope remains constant across four orders of magnitude in stellar mass.

No significant SFR dependence found in the metallicity beyond the MZR.

Systematic uncertainties do not significantly alter the MZR slope.

Abstract

We extend the stellar-mass gas-phase metallicity relation (MZR) at $z = 1.1-3.4$ down to the extremely low-mass regime using 183 galaxies with $\log(M_*/M_\odot) = 6.3-10.2$, based on deep JWST/NIRISS slitless spectroscopy from the NGDEEP program. The derived MZR is in excellent agreement with our previous result from 50 galaxies in the GLASS-JWST sample, underscoring the robustness and universality of this relation. Together, these datasets constitute the largest sample of dwarf galaxies yet obtained with NIRISS. The observed MZR slope, $\beta\simeq0.24\pm0.03$, remains constant across nearly four orders of magnitude in stellar mass. Analytical modeling of the metal-loading factor of outflows ($\zeta_\textrm{out}$) indicates that, at $M_*\lesssim10^8M_\odot$, $\zeta_\textrm{out}$ becomes progressively less dominant than the gas fraction ($\mu_\textrm{gas}$) in regulating the MZR slope. Using this enlarged NIRISS sample, we further test the existence of the fundamental metallicity relation (FMR). We find no robust evidence for an additional SFR dependence beyond the MZR, nor any reduction in metallicity scatter when SFR is included. Examination of systematic uncertainties in \oh, $M_*$ and SFR suggests that the MZR slope ($\beta\sim0.22$) is robust, and that different assumptions about the strong-line calibrations or star-formation history (SFH) of the galaxies change the slope by less than 1-$\sigma$. At the current depth of the NIRISS data, evidence for an FMR among high-redshift dwarf galaxies remains inconclusive, highlighting the need for larger samples, and deeper observations.