Tracing ionized gas kinematics in Lyman-Break Analogs. Implications for star formation compactness and outflow properties

TL;DR

This study investigates ionized gas kinematics and feedback in local Lyman Break Analogs, revealing complex outflows driven by star formation that resemble high-redshift starburst behaviors, with implications for galaxy evolution.

Contribution

It provides detailed kinematic modeling of ionized gas in local analogs, demonstrating the link between star formation compactness and outflow strength, a novel insight into feedback processes.

Findings

Ionized outflows have velocities of 200-500 km/s.

Mass outflow rates range from 0.20 to 2.72 solar masses per year.

Stronger outflows are associated with higher star-formation-rate surface density.

Abstract

We present a study of the ionized gas kinematics and feedback properties in a sample of 14 low-mass, UV-luminous Lyman Break Analogs (LBAs) at redshifts z~0.1-0.3. These compact, strongly star-forming galaxies serve as local analogs of high-redshift starbursts. Using high-resolution VLT/X-shooter spectra, we model the optical emission-line profiles, including [O III] 4959,5007 and the Balmer lines, with multi-component Gaussian fits. All galaxies show complex kinematics that require both narrow (sigma < 90 km/s) and broad (sigma > 90 km/s) components. The narrow components trace highly turbulent gas associated with massive star-forming regions, while the broad components indicate ionized outflows driven by stellar winds and supernova feedback, with outflow velocities of about 200-500 km/s. Estimated mass outflow rates range from 0.20 to 2.72 solar masses per year, with mass-loading factors between 0.03 and 0.81. We find a mild increase in mass loading toward lower stellar masses, as well as a strong correlation between mass loading and star-formation-rate surface density, suggesting that more compact starbursts drive more powerful outflows. These trends are consistent with those seen in star-forming galaxies at higher redshifts. Our results highlight the importance of local UV-compact starbursts for understanding feedback processes in low-mass, rapidly star-forming galaxies.