cautionary tale of Ly C escape fraction estimates from high-redshift galaxies.

Measuring the escape fraction, f esc, of ionizing, Lyman continuum (Ly C) radiation is key to our understanding of the process of cosmic reionization. In this paper, we provide a methodology for recovering the posterior probability distribution of the Ly C escape fraction, |$f_{\rm esc}^{\rm PDF}$|⁠ , considering both the observational uncertainties and ensembles of simulated transmission functions through the intergalactic medium (IGM). We present an example of this method applied to a VUDS galaxy at z = 3.64 and find |$f_{\rm esc}^{\rm PDF}$| = 0.51 |$^{+0.33}_{-0.34}$| and compare this to the values computed assuming averaged IGM transmission with and without consideration of detection bias along average sightlines yielding |$f_{\rm esc}^{\langle T \rangle }$| = 1.40 |$^{+0.80}_{-0.42}$| and |$f_{\rm esc}^{\rm bias}$| = 0.82 |$^{+0.33}_{-0.16}$|⁠. Our results highlight the limitations of methods assuming average, smooth transmission functions. We also present MOSFIRE data for a sample of seven Ly C candidates selected based on photometric redshifts at z > 3.4, but find that all seven have overestimated photometric redshifts by Δ z ∼ 0.2 making them unsuitable for Ly C measurements. This results likely due to a bias induced by our selection criteria. [ABSTRACT FROM AUTHOR]