EPoS Contribution
EPoS Contribution
Modelling C-Type Shock Waves in Dense Clouds

Aleksandr Nesterenok
Ioffe Inst., Saint-Petersburg, RU
The observations of the outflows associated with star formation provide valuable information on the chemical composition of the medium surrounding protostars and on the process of star formation itself. The gas flows from accreting protostar meet the surrounding envelope or interstellar medium and shocks form. We present the model of steady, transverse C-type shocks in dense interstellar environment. The full gas-grain chemical network is taken into account in simulations: gas-phase chemistry, adsorption of gas species on dust grains, various desorption mechanisms, grain surface chemistry, ion neutralization on dust grains, sputtering of grain mantles in shock. The simulations consist of two steps: (i) modelling of the chemical and thermal evolution of the static molecular cloud and (ii) shock simulations. The focus of the paper is on the chemical processing of gas material and grain mantles in the shock. The dust heating in shock results in complex chemistry on dust grain surface. Complex organic molecules such as methyl formate can be produced on warm dust in the shock region before sputtering process takes place. The sputtering of ice mantles takes place in the shock region close to the temperature peak of neutral gas. At high shock speeds, molecules ejected from grain mantles are effectively destroyed in hot gas and their survival time is low, of the order of dozens of years. The shock model presented can be employed to study molecular emission from shocked gas in protostellar outflows.
Caption: Abundances of some complex organic molecules relative to hydrogen nuclei in C-type shock, s-X denotes species X in icy mantles of dust grains. Preshock gas density is nH2 = 104 cm-3. Results are shown for shock velocities 20 km s-1 - upper graphs, and 30 km s-1 - lower graphs.
Suggested Session: Chemistry