Orion-Eridanus region at different wavelengths. The color scale of these images has been manipulated to make the structures present stand out better. Panel A: overall Orion-Eridanus Region under study. Colors are as in Fig. 1. The [C II] COBE extraction aperture is shown as white circle with a physical extension of ~400 pc, taking 414 pc as average distance. Panel B: FIRAS COBE [C II] map and the extractionaperture as a white circle. Panel C: HI map integrated over the velocity range −40 km s⁻¹ < ν_LSR < 40km s⁻¹ (Brown et al. 1995). Panel D: CO(J = 2−1) map from Planck. The small white circles cover those parts of the four molecular clouds (Orion Molecular A & B, λ Ori, and Mon R2) and are used in our analysis (see also Figs. 4–6). Panel E: WIM extraction aperture for Barnard’s Loop and λ Orionis. The small white circles covering these two objects identify the apertures over which we performed our analysis. Panel F: extraction aperture of M 42 from Pogge et al. (1992) is shown in white circle. Each panel has different scale size.