g′z′K_s diagram for AKARI sources with optical counterparts. (Left) blue dots represent stars identified in Sect. 5, and red dots indicate galaxies with z_p< 1.4. The dashed lines are the borders given by Eqs. (2)–(4). Bruzual & Charlot (2003) stellar population synthesis models for g′z′K_s color–color diagram with 1.4 <z_p< 2.5, which Arcila-Osejo & Sawicki (2013) show are overplotted for comparison. Ages in Gyr are shown with different colors, while different E(B − V) are represented with different line thicknesses. (Right) 1.4 <z_p< 2.5 AKARI sources are plotted in yellow. The z_p< 1.4 sources shown in the left panel are also plotted but in gray.