The Ly$α$ and Continuum Origins Survey. III. Investigating the link between galaxy morphology, merger properties and LyC escape

Characterizing the mechanisms and galaxy properties conducive to the emission and escape of ionizing (LyC) emission is necessary to accurately model the Epoch of Reionization, and identify the sources that powered it. The Lyman-alpha and Continuum Origins Survey (LaCOS) is the first program to obtain uniform, multi-wavelength sub-kpc imaging for a sufficiently large sample (42) of galaxies observed in LyC to enable statistically robust studies between LyC and resolved galaxy properties. Here, we characterize the morphology and galaxy merger properties of LaCOS galaxies and investigate their connection with the escape fraction of LyC emission fescLyC. We find strong anti-correlations between fescLyC and radii (r₂₀, r₅₀, and r₈₀) measured in filters containing emission from star-forming regions, and with the asymmetry and clumpiness in F150LP, the bluest filter in our dataset, tracing UV continuum and Ly$α$. We find that ≥48% of LaCOS galaxies are visually classified as galaxy mergers. In LyC-emitters, ≥41% of the galaxies are galaxy mergers, LyC-emitting mergers have fescLyC=0-16%. Galaxies robustly identified as mergers in LaCOS are all at advanced stages of interaction, close to coalescence. The fescLyC properties of mergers and non-mergers cannot be differentiated statistically, and we only find significant difference between the two populations in terms of their sizes, with mergers having larger sizes. We conclude that fescLyC tends to be larger in galaxies with a small number of compact, centrally-located, UV-emitting star-forming regions, that merger represent a sizable fraction of LyC-emitting samples at z~0, and that mergers at advanced stages of interaction can facilitate the escape of LyC photons from galaxies.