tokens: at best, lower limits to the the true integrated fraction of escaping ionizing photons, and generally offer poor representations of the total number of ionizing photons that escape. The tables in Figure 4 show that LBGs may emit significant amounts of LyC radiation, at the level of 5%–1%, even if the optical depth at the edge is ≈10 (). By way of example, we note that Izotov et al. ( 2016a ) found an edge escape fraction f e 900 = 0.08. Using Equation ( 8 ), we derived an integrated escape fraction of f e LyC = 0.35 or 0.25 for our two cases, respectively. This suggests that the “f-escape” problem might not be as bad as it seems. The only definitive way to rule this out is through deep UV observations in the redshifted rest frame of the EUV in an attempt to observe the LyC drop-in. In the next section we address the observability of the Lyman drop-ins in the face of the steadily increasing mean optical depth of the IGM with increasing redshift. 4. Redshifted Models, Including Mean IGM Transmission We have thus far not included attenuation of the escaping LyC due to resonant scattering and photoelectric absorption (photoionization) from discrete collections of intervening clouds in the IGM. Here we use the rest frame LyC transmission models described in Section 3.1 to compute the mean transmission of the IGM as a function of the fiducial redshifts in Table 1 . The mean transmission function is derived from a mean optical depth (Paresce et al. 1980 ; Madau 1995 ; Inoue et al. 2014 ), expressed here as a numeric integral:Here, the observed wavelength is related to the rest frame wavelength by . The optical depth is . The redshift range from is in fixed increments of . The logarithm of the column densities range from in variable increments of with 0 . The differential distribution of the number of discrete absorbers with respect to H i column density and redshift, , is typically characterized by a piecewise continuous function in redshift and column density (c.f. Madau 1995 ; Inoue et al. 2014 ). There are three basic H i absorption regimes: the Ly α forest regime (LAF), ; the Lyman limit (LL) regime, , and the damped Ly α (DLA) regime, . We employ the described by Inoue et al. ( 2014 ), which uses a “Schechter-like” distribution function for the column density multiplied by a piecewise-continuous multiple power law distribution to describe the evolution in redshift. The distribution function is broken down into the sum of two different products, which in combination reasonably agrees with the evolution of H i absorption systems from the LLA to DLA regimes as detailed in the literature (Weymann et al. 1998 ; Prochaska et al. 2005 , 2010 ; Ribaudo et al. 2011 ; Noterdaeme et al. 2012 ; Fumagalli et al. 2013 ; Kim et al. 2013 ; O’Meara et al. 2013 ; Prochaska et al. 2014 ). We note that the Inoue et al. ( 2014 ) distribution function produces a mean transmission that is generally less aggressive than that produced by the distribution function
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