Evaporation and condensation processes of giant molecular clouds in a hot plasma

2D hydrodynamical simulations are performed to examine the evaporation and condensation processes of giant molecular clouds in the hot phase of the interstellar medium. The evolution of cold and dense clouds (T = 1000 K, nH = 3 cm , M = 6 ·10 M⊙) is calculated in the subsonic stream of a hot tenuous plasma (T = 5 · 10 K, nH = 6 · 10 −4 cm). Our code includes self-gravity, heating and cooling processes and heat conduction by electrons. The thermal conductivity of a fully ionized hydrogen plasma (κ ∝ T) is applied as well as a saturated heat flux in regions where the mean free path of the electrons is large compared to the temperature scaleheight. Significant differences occur between simulations with and without heat conduction. In the simulations without heat conduction, the clouds outermost regions is stired up by Kelvin-Helmholtz (KH) instability after only a few dynamical times. This prevents an infiltration of a significant amount of hot gas into the cloud before its destruction. In contrast, models including heat conduction evolve less violently. The boundary of the cloud remains nearly unsusceptible to KH instabilities. In this scenario it is possible to mix the formerly hot streaming gas very effectively with the cloud material.