IGM Transmission Bias for $z$ $\geq$ 2.9 Lyman Continuum Detected
  Galaxies
  Understanding the relationship between the underlying escape fraction of
Lyman continuum (LyC) photons ($f_{\rm esc}$) emitted by galaxies and measuring
the distribution of observed $f_{\rm esc}$ values at high redshift is
fundamental to the interpretation of the reionization process. In this paper we
perform a statistical exploration of the attenuation of LyC photons by neutral
hydrogen in the intergalactic medium using ensembles of simulated transmission
functions. We show that LyC detected galaxies are more likely to be found in
sightlines with higher-than-average transmission of LyC photons. This means
that adopting a mean transmission at a given redshift leads to an overestimate
of the true $f_{\rm esc}$ for LyC detected galaxies. We note, however, that
mean values are appropriate for $f_{\rm esc}$ estimates of larger parent
samples that include LyC non-detected galaxies. We quantify this IGM
transmission bias for LyC detections in photometric and spectroscopic surveys
in the literature and show that the bias is stronger for both shallower
observations and for fainter parent samples (i.e. Lyman $\alpha$ emitters
versus Lyman break galaxies). We also explore the effects of varying the
underlying probability distribution function (PDF) of $f_{\rm esc}$ on
recovered values, showing that the underlying $f_{\rm esc}$ PDF may depend on
sample selection by comparing with observational surveys. This work represents
a first step in improved interpretation of LyC detections in the context of
understanding $f_{\rm esc}$ from high redshift galaxies.
