EPoS Contribution
EPoS Contribution
Molecular Tracers of Turbulent Shocks in Giant Molecular Clouds

Andy R. Pon
University of Victoria, Victoria, Canada
We are investigating the manner in which energy flows through, into, and out of molecular clouds in order to better understand how energy is conserved throughout a cloud's lifetime. For example, we examine the dissipation of turbulent energy through shocks. Current numerical simulations show that the turbulent energy of a GMC dissipates on the order of a crossing time but do not explicitly follow how this energy is released. We have run models of shocks, appropriate for the conditions inside of a GMC, to determine which species and transitions dominate the cooling and radiative energy release. Combining models of shock emission and models, which compute the rate of turbulent energy dissipation, we can make predictions for the strongest tracers. Given the conditions in nearby molecular clouds, we predict those line emissions that will be observable with current and upcoming observational facilities such as Herschel, SOFIA and ALMA.
Caption: The attached figure shows the relative strengths of various molecular transitions as calculated from the shock models of Kaufman and Neufeld (1996). The shock velocities and initial densities of the gas for the models are given along the top and left sides of the grid respectively. Each grid box has been scaled to the flux of the most intense line in that grid box and the flux of the strongest line is given, in ergs/s/cm^2, in the top left corner of each box. Note how the CO lines dominate for the lowest density and velocity and how the H_2 and H_2O lines become significant for higher densities and shock velocities. Thus, the presence or absence of strong H_2 and H_2O lines could be used to constrain the properties of the shocks in a molecular cloud. The ratios of the different CO lines not only can also be used to constrain density and velocity but they can also be used to differentiate between shock emission and emission from PDRs and the ambient cool gas in molecular clouds. We are currently planning to extend these models to lower densities and shock velocities, which are more appropriate for molecular clouds. Other molecular species, which are not major shock coolants, can also be easily added into these models to provide further diagnostics for the shock conditions.
Collaborators:
D. Johnstone, NRC-HIA, Canada
M.J. Kaufman, San Jose State U, USA
Key publication

Suggested Session: Molecular Clouds, Turbulence