2017ApJ...850...23B

We present calculations of molecular, atomic, and ionic line emission from simulations of giant molecular cloud (GMC) collisions. We post-process snapshots of the magnetohydrodynamical simulations presented in an earlier paper in this series by Wu et al. of colliding and non-colliding GMCs. Using photodissociation region (PDR) chemistry and radiative transfer, we calculate the level populations and emission properties of the transitions of ¹²CO J = 1-0, [C I] ³P₁→³P₀ at 609 µm, [C II] 158 µm, and [O I] ³P₁→³P₀ at 63 µm. From emission maps of integrated intensity and position-velocity diagrams, we find that fine-structure lines, particularly [C II] 158 µm, can be used as a diagnostic tracer for cloud-cloud collision activity. These results hold even in more evolved systems in which the collision signature in molecular lines has been diminished.