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Register a new userGMC Collisions as Triggers of Star Formation. I. Parameter Space Exploration with 2D Simulations
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Benjamin Wu
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We utilize magnetohydrodynamic (MHD) simulations to develop a numerical model for GMC-GMC collisions between nearly magnetically critical clouds. The goal is to determine if, and under what circumstances, cloud collisions can cause pre-existing magnetically subcritical clumps to become supercritical and undergo gravitational collapse. We first develop and implement new photodissociation region (PDR) based heating and cooling functions that span the atomic to molecular transition, creating a multiphase ISM and allowing modeling of non-equilibrium temperature structures. Then in 2D and with ideal MHD, we explore a wide parameter space of magnetic field strength, magnetic field geometry, collision velocity, and impact parameter, and compare isolated versus colliding clouds. We find factors of ~2-3 increase in mean clump density from typical collisions, with strong dependence on collision velocity and magnetic field strength, but ultimately limited by flux-freezing in 2D geometries. For geometries enabling flow along magnetic field lines, greater degrees of collapse are seen. We discuss observational diagnostics of cloud collisions, focussing on 13CO(J=2-1), 13CO(J=3-2), and 12CO(J=8-7) integrated intensity maps and spectra, which we synthesize from our simulation outputs. We find the ratio of J=8-7 to lower-J emission is a powerful diagnostic probe of GMC collisions.
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We simulate the collision of two Giant Molecular Clouds (GMCs) using the movingmesh magnetohydrodynamical (MHD) code AREPO. We perform a small parameterspace study on how GMC collisions affect the star formation rate (SFR). The pa-rameters we consider are relative velocity, magnetic field inclination and simulationresolution. From the collsional velocity study we find that a faster collision causes starformation to trigger earlier, however, the overall trend in star formation rate integratethrough time is similar for all. This contradicts the claim that the SFR significantlyincreases as a result of a cloud collision. From varying the magnetic field inclinationwe conclude that the onset of star formation occurs sooner if the magnetic field isparallel to the collisional axis. Resolution tests suggests that higher resolution delaysthe onset of star formation due to the small scale turbulence being more resolved.
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