Monday, July 29, 2013

1307.6868 (Ugo Hincelin et al.)

Survival of interstellar molecules to prestellar dense core collapse and early phases of disk formation    [PDF]

Ugo Hincelin, Valentine Wakelam, Benoît Commerçon, Franck Hersant, Stéphane Guilloteau
An outstanding question of astrobiology is the link between the chemical composition of planets, comets and other Solar System bodies and the molecules formed in the interstellar medium. Understanding the chemical and physical evolution of the matter leading to the formation of protoplanetary disks is an important step for this. We bring some new stones to this longstanding problem using three-dimensional chemical simulations of the early phases of disk formation: we interfaced the full gas-grain chemical model Nautilus with the radiation-magneto-hydrodynamic model RAMSES, for different configurations and intensities of magnetic field. Our results show that the chemical content (gas and ices) is globally conserved during the collapsing process, from the parent molecular cloud to the young disk surrounding the first Larson core. A qualitative comparison with cometary composition suggests that comets are constituted of different phases, some molecules being direct tracers of interstellar chemistry, while others, including complex molecules, seem to have been formed in disks, where higher densities and temperatures allow for an active grain surface chemistry. The latter phase, and its connection with the formation of the first Larson core, remains to be modelled.
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