tokens: constrain the escape fraction of the ionizing radiation and/or the presence of faint satellite galaxies during the late stages of cosmic reionization. We have predicted radial surface brightness profiles that include the contribution from (i) fluorescent emission powered by ionizing radiation leaking from the central galaxy (as in Mas-Ribas Dijkstra 2016 , for two different CGM prescriptions), and (ii), nebular emission from faint satellite sources that possibly resided within the halo of the central galaxies (as in Mas-Ribas et al. 2017 ). We have compared our predictions with observations of Ly α halos at z = 5.7 and z = 6.6, and have also predicted H α and visible continuum surface brightness profiles may be detectable within future JWST observations. We present and discuss our findings below. 1. Our comparison of models to observations favors the model with a very low escape fraction of ionizing radiation, , from galaxies within the range of magnitudes . This scenario implies that these galaxies do not contribute significantly to the reionization process. Therefore, if galaxies are the major contributors to the reionization process, as recently restated by Parsa et al. ( 2017 ), a large population of faint sources with a high ionizing escape fraction is necessary. 2. The presence of faint satellite sources is unclear. Two out of four comparisons with current Ly α data indicate that satellite sources might contribute to the extended Ly α emission, but the effect of systematics and uncertainties in the observations do not allow for a clear conclusion. Given the required existence of faint sources driven by the low escape fraction results, if the presence of satellite sources around brighter galaxies is ruled out by the observations, this might imply that the population of faint objects is spread out within the IGM, making its detection more challenging. 3. JWST will be able to probe the ionizing escape fraction from one bright, galaxy up to distances of a few tens of pkpc from the center. Fainter galaxies and/or a high S/N for the continuum observations require the observation and stacking of several objects. We stress that we have adopted and extrapolated two CGM models that were derived to match observables at redshifts around . The validity of our results therefore depends on the ability of these two models to realistically describe the medium surrounding galaxies. While a more detailed parameterization of the CGM at high redshift (if currently feasible) is beyond the scope of our work, future observations of extended emission, together with absorption studies (e.g., Dijkstra Kramer 2012 ; Hennawi Prochaska 2013 ; Prochaska et al. 2013 , see also Steidel et al. 2010 , 2011 ), will clearly enable us to use our proposed method to further constrain the escape fraction. The prospects for doing this experiment at lower redshifts, , are interesting, as the surface brightness for emission lines depends on redshift as . However, the contribution
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