The leakage of Lyman-continuum photons from a major merger at $z\sim1$

TL;DR

This study reports the first detection of Lyman-continuum photons from a major galaxy merger at redshift ~1, suggesting such systems significantly contribute to the universe's ionizing photon budget during peak merger activity.

Contribution

It provides the first observational evidence of LyC leakage from a major merger at z~1, combining multi-wavelength imaging and kinematic data to support the merger hypothesis.

Findings

Detected LyC photons from a z=1.097 merger system.

Estimated >8% ionizing photon escape fraction.

Identified the system as a major merger with a mass ratio of 1.13.

Abstract

We report the detection of Lyman-continuum (LyC) photons from a massive interacting system at $z=1.097$ in the Hubble Ultra Deep Field. The LyC detection is made in the far-ultraviolet F154W band of the UVIT telescope onboard AstroSat. Both JWST and HST imaging of the system reveal signs that it is a likely merger. In particular, high-resolution imaging in the JWST bands reveals an infrared luminous object within the system that is faint in the bluer HST bands. The ionized-gas kinematics from the MUSE-UDF data supports the merger hypothesis. We estimate that the entire system is leaking more than $8 \%$ of its ionizing photons to the intergalactic medium. The SED-derived stellar masses of the two components indicate that this is a major merger with a mass ratio of ${1.13 \pm 0.37}$. This detection hints at the potential contribution of massive interacting systems at higher redshifts, when major mergers were more frequent, to the ionizing budget of the universe.