Multivariate Predictors of LyC Escape II: Predicting LyC Escape Fractions for High-Redshift Galaxies

TL;DR

This study develops empirical multivariate models to predict the escape fraction of ionizing photons from high-redshift galaxies, using low-redshift data and survival analysis, aiding understanding of reionization.

Contribution

It introduces new multivariate predictive models for LyC escape fractions based on low-redshift data and applies them to high-redshift galaxies, improving accuracy over single-variable methods.

Findings

Models reproduce observed escape fractions at z~3

Predicted median escape fraction for high-z galaxies is 0.047-0.14

At least 33% of high-z galaxies may have escape fractions >0.2

Abstract

JWST is uncovering the properties of ever increasing numbers of galaxies at z>6, during the epoch of reionization. Connecting these observed populations to the process of reionization requires understanding how efficiently they produce Lyman continuum (LyC) photons and what fraction (fesc) of these photons escape into the intergalactic medium. By applying the Cox proportional hazards model, a survival analysis technique, to the Low-redshift Lyman Continuum Survey (LzLCS), we develop new, empirical, multivariate predictions for fesc. The models developed from the LzLCS reproduce the observed fesc for z~3 samples, which suggests that LyC emitters may share similar properties at low and high redshift. Our best-performing models for the z~3 galaxies include information about dust attenuation, ionization, and/or morphology. We then apply these models to z$\gtrsim$6 galaxies. For large photometric samples, we find a median predicted fesc=0.047-0.14. For smaller spectroscopic samples, which may include stronger emission line galaxies, we find that $\geq$33% of the galaxies have fesc >0.2, and we identify several candidate extreme leakers with fesc $\geq$0.5. The current samples show no strong trend between predicted fesc and UV magnitude, but limited spectroscopic information makes this result uncertain. Multivariate predictions can give significantly different results from single variable predictions, and the predicted fesc for high-redshift galaxies can differ significantly depending on whether star formation rate surface density or radius is used as a measure of galaxy morphology. We provide all parameters necessary to predict fesc for additional samples of high-redshift galaxies using these models.