RELICS: Small Lensed \(z\geq5.5\) Galaxies Selected as Potential Lyman Continuum Leakers

Abstract

We present size measurements of 78 high-redshift (\(z\geq 5.5\)) galaxy candidates from the Reionisation Lensing Cluster Survey (RELICS). These distant galaxies are well-resolved due to the gravitational lensing power of foreground galaxy clusters, imaged by the Hubble Space Telescope (HST) and the Spitzer Space Telescope. We compute sizes using the forward-modeling code Lenstruction and account for magnification using public lens models. The resulting size-magnitude measurements confirm the existence of many small (\(R_{\rm{eff}}<200\) pc) galaxies in the early universe, in agreement with previous studies. In addition, we highlight compact and highly star-forming sources as possible Lyman continuum leaker candidates with high inferred [OIII]+H\(\beta\) that could be major contributors to the process of reionisation. Future spectroscopic follow-up of these compact galaxies (e.g., with the James Webb Space Telescope) will further clarify their role in reionisation and the physics of early star formation.