Multivariate Predictors of Lyman Continuum Escape. II. Predicting Lyman Continuum Escape Fractions for High-redshift Galaxies
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 (f esc) 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 f esc. The models developed from the LzLCS reproduce the observed f esc 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 ≳ 6 galaxies. For large photometric samples, we find a median predicted f esc = 0.047–0.14. For smaller spectroscopic samples, which may include stronger emission-line galaxies, we find that ≥33% of the galaxies have f esc > 0.2, and we identify several candidate extreme leakers with f esc ≥ 0.5. The current samples show no strong trend between predicted f esc 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 f esc 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 f esc for additional samples of high-redshift galaxies using these models. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-15626, GO-13744, GO-14635, GO-15341, and GO-15639.
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