On the Connection between the O32 Ratio and LyC Escape

Abstract

Identifying Lyman continuum (LyC) leaking galaxies is an important step towards understanding the reionization history of the Universe. However, measuring the escape fraction of LyC photons ( f _LyC ) in high- z galaxies is a very challenging task. We examine whether the O32 ratio, defined as the ratio between [OIII] λ5007Å and [OII] λ3727Å lines, can be used as a proxy for f _LyC . To this end, we construct synthetic spectra by post-processing high-resolution, radiation-hydrodynamic simulations of giant molecular clouds (GMCs) with the photo-ionization code, CLOUDY. We then combine the results with a random forest machine learning algorithm to calculate emission line strengths at different evolutionary phases of the GMC.