GA-NIFS: high prevalence of dusty and metal-enriched outflows in massive and luminous star-forming galaxies at $z\sim3-9$

TL;DR

This study uses JWST data to analyze ionized outflows in massive, luminous star-forming galaxies at high redshift, revealing dust and metal enrichment but limited escape velocities, implying weak feedback effects on star formation.

Contribution

First detailed characterization of ionized outflows in high-mass, high-luminosity galaxies at z~3-9 using JWST/NIRSpec, expanding understanding of feedback in early massive galaxies.

Findings

Outflows are dustier and more metal-enriched than the ISM.

Outflow velocities are insufficient for escape, mainly redistributing dust and metals.

Weak mass-loading factors suggest limited suppression of star formation.

Abstract

We present a search for and characterization of ionized outflows in 15 star-forming systems at $z\sim3-9$ with no evidence of Active Galactic Nuclei (AGN), observed with JWST/NIRSpec IFU as part of the GA-NIFS program. The targets often show satellites and complex substructure, from which we isolate 40 galaxies/regions. The sample probes the high-mass end of the galaxy population, with most sources having log$_{10}$~(M$_\star$/M$_\odot$)=$9.5-11$, extending previous studies on high-z star formation driven outflows that mainly focused on lower-mass galaxies. Using the [OIII]5007 and H$\alpha$ emission lines, we identify broad kinematic components consistent with galactic outflows in 14 galaxies/regions. We find that the outflowing gas is more dust attenuated (by $A_{\rm V}$$\sim0.59$ mag on average) and metal-enriched (0.13 dex) than the interstellar medium (ISM) of the host galaxies, but its velocities are insufficient to escape the galaxies and reach the circumgalactic medium, suggesting that outflows mainly redistribute dust and metals around their hosts. The outflows identified in this study display velocity dispersions within $\sigma_{\rm out}=130-340$~km~s$^{-1}$ and outflow velocities $v_{\rm out}=170-600$~km~s$^{-1}$, and, when combined with less luminous and less massive star-forming galaxies from previous works, reveal a statistically significant correlation between $v_{\rm out}$ and star formation rate (SFR). The typically low mass-loading factors ($\eta=\dot{M}_{\rm out}/SFR$$\leq1$, in 9 out of 14 the outflows) indicate that these outflows do not strongly suppress star formation. Overall, our results suggest that ejective feedback via ionized outflows is inefficient in massive, luminous star-forming galaxies within the first 2 Gyr of the Universe.