Lyman Break Analogs: Constraints on the Formation of Extreme Starbursts at Low and High Redshift

TL;DR

This study investigates local Lyman Break Analogs (LBAs) to understand their starburst formation mechanisms, comparing their properties to high-redshift Lyman Break Galaxies (LBGs), and examines the role of mergers and gas content in their evolution.

Contribution

The paper provides detailed kinematic and morphological analysis of LBAs, highlighting the challenges in identifying merger events and exploring the role of gas fractions in starburst formation.

Findings

LBAs share kinematic properties with high-redshift LBGs.

Merger identification is complicated by observational limitations.

Gas fractions influence whether mergers can produce observed properties.

Abstract

Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe ($z\sim 0.2$), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS, which shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies alone are not an appropriate diagnostic to rule out merger events as the trigger for the observed starburst. Comparison between the kinematic analysis and morphological indices from HST imaging illustrates the difficulties of properly identifying (minor or major) merger events, with no clear correlation between the results using either of the two methods. Artificial redshifting of our data indicates that this problem becomes even worse at high redshift due to surface brightness dimming and resolution loss. Whether mergers could generate the observed kinematic properties is strongly dependent on gas fractions in these galaxies. We present preliminary results of a CARMA survey for LBAs and discuss the implications of the inferred molecular gas masses for formation models.