GMC Collisions as Triggers of Star Formation. V. Observational Signatures

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] 3 P 1 → 3 P 0 at 609 μm, [C ii] 158 μm, and [O i] 3 P 1 → 3 P 0 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.