Ionized gas kinematics and chemical abundances of low-mass star-forming galaxies at z 3

Context. Feedback from massive stars plays a crucial role in regulating the growth of young star-forming galaxies (SFGs) and in shaping their interstellar medium (ISM). This feedback contributes to the removal and mixing of metals via galactic outflows and to the clearance of neutral gas, which facilitates the escape of ionizing photons. Aims. Our goal is to study the impact of stellar feedback on the chemical abundances of the ISM in a sample of SFGs with strong emission lines at z similar to 3. Methods. We selected 35 low-mass SFGs (7:9 < log(M star M circle dot) < 10:3) from deep spectroscopic surveys based on their CIII]lambda 1908 emission. We used new follow-up near-infrared (NIR) observations to examine their rest-optical emission lines and to identify ionized outflow signatures through broad emission line wings detected after Gaussian modeling of [OIII]lambda lambda 4959,5007 profiles. We characterized the gas-phase metallicity and carbon-to-oxygen (C /O) abundance of the galaxies using a Te-based method via the OIII]lambda 1666 /[OIII]lambda 5007 ratio and photoionization models. Results. We find line ratios and rest-frame equivalent widths (EWs) characteristic of high-ionization conditions powered by massive stars. Our sample displays a mean rest-frame EW([OIII]lambda 5007) of similar to 560 angstrom, while about 15% of the SFGs show EW([OIII]lambda lambda 4959,5007) > 1000 angstrom and EW(CIII]) > 5 angstrom, closely resembling those now seen in epoch of reionization (EoR) galaxies with the James Webb Space Telescope. We find high T-e values, which imply low gas-phase metallicities 12 +log(O/H) similar to 7.5-8.5 (mean of 17% solar) and C /O abundances from 23% to 128% solar, with no apparent increasing trend with metallicity. Our sample follows the mass-metallicity relation at z similar to 3, with some galaxies showing lower gas-phase metallicities. This results in significant deviations from the fundamental metallicity relation. From our [OIII]lambda lambda 4959,5007 line profile modeling, we find that 65% of our sample shows an outflow component, which is found both blue- or redshifted relative to the ionized gas systemic velocity, and the mean maximum velocities are upsilon(max) similar to 280 km s(-1). We find a weak correlation between v max and the star formation rate surface density (Sigma(SFR)) of upsilon(max) = (2:41 +/- 0:03) x Sigma((0:06 +/- 0:03))(SFR) . Moreover, we find that the mass-loading factor mu of our galaxy sample is typically lower than in more massive galaxies from the literature, but it is higher than in typical local dwarf galaxies. In the stellar mass range covered by our sample, we find that mu increases with Sigma(SFR). This suggests that for a given stellar mass, denser starbursts in low-mass galaxies produce stronger outflows. Our results complement the picture drawn by similar studies at lower redshift, suggesting that the removal of ionized gas in low-mass SFGs driven by stellar feedback is regulated by their stellar mass and by the strength and concentration of their star formation, that is, Sigma(SFR).