Star-forming galaxies are though to be a strong candidate of the primary source of the cosmic reionization. However, its emissivity in the Lyman continuum is quite uncertain yet, because the direct detection of the Lyman continum from distant galaxies is still very challenging issue due to the intergalactic hydrogen absorption. Here, we discuss how far galaxies we can detect the Lyman continuum from.
Based on a Monte Carlo simulation to model the stochastic intergalactic absorption, we have found that the probability having a clean line-of-sight for z~4 galaxies is about 20%. However, the probability for z>4 galaxies rapidly decreases, then, the direct detection of their Lyman continuum is virtually impossible.