VALES VIII: Weak ionized gas outflows in star-forming galaxies at $z \sim 0.15$ traced with VLT/MUSE

TL;DR

This study investigates ionized gas outflows in 15 low-redshift star-forming galaxies using VLT/MUSE data, revealing modest feedback effects that slightly inhibit star formation and are dominated by stellar radiation rather than shocks.

Contribution

First detailed analysis of ionized outflows in low-redshift galaxies using integral field spectroscopy combined with broadband SED fitting.

Findings

Outflows have a mass outflow rate of about 0.1 solar masses per year.

Feedback appears weak, with low kinetic power and mass loading factors.

Star formation is mainly driven by stellar radiation, not shocks.

Abstract

We characterize the ionized gas outflows in 15 low-redshift star-forming galaxies, a Valpara\'iso ALMA Line Emission Survey (VALES) subsample, using MUSE integral field spectroscopy and GAMA photometric broadband data. We measure the emission-line spectra by fitting a double-component profile, with the second and broader component being related to the outflowing gas. This interpretation is in agreement with the correlation between the observed star-formation rate surface density ($\Sigma_{\mathrm{SFR}}$) and the second-component velocity dispersion ($\sigma_{\mathrm{2nd}}$), expected when tracing the feedback component. By modelling the broadband spectra with spectra energy distribution (SED) fitting and obtaining the star-formation histories of the sample, we observe a small decrease in SFR between 100 and 10 Myr in galaxies when the outflow H$\alpha$ luminosity contribution is increased, indicating that the feedback somewhat inhibits the star formation within these timescales. The observed emission-line ratios are best reproduced by photoionization models when compared to shock-ionization, indicating that radiation from young stellar population is dominant, and seems to be a consequence of a continuous star-formation activity instead of a bursty event. The outflow properties such as mass outflow rate ($\sim 0.1\,$M$_\odot$ yr$^{-1}$), outflow kinetic power ($\sim 5.2 \times 10^{-4}\% L_{\mathrm{bol}}$) and mass loading factor ($\sim 0.12$) point towards a scenario where the measured feedback is not strong and has a low impact on the evolution of galaxies in general.