Coreshine ratio versus 3.6 μm intensity in the Taurus-Perseus direction. Zoom on the starless core cases, full range is displayed in Fig. 14 – Difference between M_high (upper row) and M_low (lower row) modeling without internal source for the two background fractions (95%, bg1, left, 75%, bg2, right). Observations – red circles: starless cores; yellow stars: cores with YSOs. Models – black squares: single grain population; blue squares: carbonates bigger than silicates in at least one of the two layers; purple squares: silicates bigger than carbonates in at least one of the two layers; green triangles: everything else. Grain model names refer to Table 3 for spatially constant grain size distribution.