Molecular line signatures of cloud-cloud collisions

Abstract

Collisions between interstellar gas clouds are potentially an important mechanism for triggering star formation. This is because they are able to rapidly generate large masses of dense gas. Observationally, cloud collisions are often identified in position-velocity (PV) space through bridging features between intensity peaks, usually of CO emission. Using a combination of hydrodynamical simulations, time-dependent chemistry, and radiative transfer, we produce synthetic molecular line observations of overlapping clouds that are genuinely colliding, and overlapping clouds that are just chance superpositions. Molecules tracing denser material than CO, such as NH${}_3$ and HCN, reach peak intensity ratios of $0.5$ and $0.2$ with respect to CO in the `bridging feature' region of PV space for genuinely colliding clouds. For overlapping clouds that are just chance superpositions, the peak NH${}_3$ and HCN intensities are co-located with the CO intensity peaks. This represents a way of confirming cloud collisions observationally, and distinguishing them from chance alignments of unrelated material.

7 pages, 4 figures, MNRAS accepted

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Cited by in corpus (7)

• Velocity structure of the 50 pc-long NGC 6334 filamentary cloud: Hints of multiple compressions and their impact on the cloud properties?
• AFGL 5180 and AFGL 6366S: sites of hub-filament systems at the opposite edges of a filamentary cloud
• Do simulated molecular clouds look like real ones?
• Structure and Kinematics of Sh2-138 -- A distant hub-filament system in the outer Galactic plane
• Gas and star kinematics in cloud-cloud collisions
• Ionized filaments and ongoing physical processes in massive star-forming sites around l = 345.5 degree
• Ammonia mapping observations of the Galactic infrared bubble N49: Three NH${}_3$ clumps along the molecular filament