Lyman Continuum Leakers at $z>3$ in the GOODS-S Field: Mergers Dominated

TL;DR

This study reveals that most high-redshift Lyman Continuum leakers are associated with galaxy mergers or starbursts, and that their extended sizes at high redshift are influenced by observational biases, shedding light on mechanisms of ionizing photon escape.

Contribution

It demonstrates that galaxy mergers and starbursts are primary channels facilitating LyC photon escape at $z>3$, highlighting the role of galaxy morphology in reionization.

Findings

20 of 23 LyC leakers show merger signatures

High-$z$ LyC leakers are more extended than low-$z$ counterparts

Merger signatures correlate with star formation main sequence status

Abstract

Understanding the ionizing photon escape from galaxies is essential for studying Cosmic Reionization. With a sample of 23 Lyman Continuum (LyC) leakers at $3<z<4.5$ in the GOODS-S field, we investigate their morphologies using high-resolution data from the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). We find that 20 of the 23 LyC leakers show merging signatures, while the remaining 3 are starbursts. Based on our previous finding that LyC leakers are not necessarily starbursts while some are in the star formation main sequence, we further find that those in the main sequence show merger signatures. Our results suggest that LyC leakers are either starbursts or mergers, both of which can facilitate the LyC photon escape, in addition to generating more LyC photons. Furthermore, we show that high-$z$ LyC leakers are statistically more extended than those selected at low redshift, which exhibits a higher merger fraction as size increases. This is likely due to the observational bias that the spatial resolution limits the detection of high-$z$ compact galaxies, while low redshift LyC leakers are more selected as compact starbursts.