アブストラクト：
In identifying cosmic reionization sources, the ionizing photons emissivity need to be quantified. In this work, we derive the ionizing photon production efficiency ξion from 270 spectroscopically confirmed LBGs identified in the ∼ 100deg2 Subaru HSC Survey (Ono et al. 2018). We select sources at z ∼3.8–5.0 where the Hα emission line falls into the Spitzer/IRAC 3.6 μm. We derive Hα fluxes utilizing the SED fitting method and estimate the value of ξion = 25.60 ± 0.01. Based on the obtained ξion, we discuss its implications for cosmic reionization.