Lyman Continuum escaping from in-situ formed stars in a tidal bridge at z = 3

TL;DR

This study analyzes JWST and HST observations of a z=3 galaxy pair, revealing in-situ star formation in a tidal bridge with high Lyman continuum escape, shedding light on ionizing photon escape mechanisms during galaxy interactions.

Contribution

It provides the first detailed analysis of LyC escape from in-situ formed stars in a tidal bridge at high redshift, highlighting the role of galaxy interactions in ionizing photon escape.

Findings

Total LyC escape fraction of 57% from the cluster.

The star cluster is less than 6.5 Myr old, formed in situ.

Gas around the cluster has been dispersed by feedback.

Abstract

We present an analysis of archival JWST NIRSpec IFS and HST imaging observations of the z = 3 Lyman-Continuum Emitter (LCE) candidate LACES104037. We show that a nearby galaxy, denoted LACES104037-S, has a redshift offset from the main galaxy by only $\sim 450$ km/s. Together with the identification of tidal bridge features between the galaxies, this indicates that the galaxies are interacting and most likely in the early stages of a merger. We show that the restframe LCE cluster sits in a tidal bridge towards the companion, about 2.7 kpc from the galaxy's core. It is faint in non-ionizing stellar continuum, and shows faint but non-negligible H{\alpha} and [O III] emission, suggesting that much of the gas surrounding the LCE cluster has been dispersed by feedback in the shallower gravitational potential of the tidal bridge. From comparing the direct LyC escape and the local H{\alpha} emission, we find a total ionizing LyC escape fraction of $f_{\mathrm{esc}} = 57 \pm 8\%$ from the LCE cluster. We estimate the age of the LCE cluster to be $\lesssim 6.5$ Myr, indicating that the cluster must have formed in situ in the tidal bridge well after the time of closest interaction. LyC escape from tidal stripping or in-situ formed stars in tidal features would depend less on intrinsic galaxy properties than typically observed in low-z LCE surveys, and could help explain the higher cosmic escape fraction as well as the enhanced diversity of LCE galaxy properties observed at Cosmic Noon.