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Paper: Formation of Globules, Pillars, and Dense Condensations Around H II Regions
Volume: 474, Numerical Modeling of Space Plasma Flows (ASTRONUM2012)
Page: 116
Authors: Tremblin, P.; Audit, E.
Abstract: We present a new model for the formation of dense clumps and pillars around H II regions based on shocks curvature at the interface between a H II region and a molecular cloud. UV radiation leads to the formation of an ionization front and of a shock ahead. The gas is compressed between them forming a dense shell at the interface. This shell may be curved due to initial interface or density modulation caused by the turbulence of the molecular cloud. Low curvature leads to instabilities in the shell that form dense clumps while sufficiently curved shells collapse on itself to form pillars. When turbulence is high compared to the ionized-gas pressure, bubbles of cold gas have sufficient kinetic energy to penetrate into the H II region and detach themselves from the parent cloud, forming cometary globules. Using computational simulations, we show that these new models are extremely efficient to form dense clumps and stable and growing elongated structures, pillars, in which star formation might occur. The inclusion of turbulence in the model shows its importance in the formation of cometary globules. The code used for the simulation is the HERACLES code, that comprises hydrodynamics with various equation of state, radiative transfer, gravity, cooling and heating. We also present observational diagnostic of these new models based on the line-of-sight velocity profiles and probability density functions.
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