title: Chemistry in the ISM and disks on the verge of planet formation
creator: Vasyunin, Anton
subject: 520
subject: 520 Astronomy and allied sciences
description: The general purpose of the thesis work is to improve astrochemical models in the era of ALMA.  This era is characterized by the active study of protoplanetary disks and the search for extraterrestrial life. First, we study how uncertainties in the rate coefficients of chemical reactions affect the abundances and column densities of key molecules in protoplanetary disks. We isolate a group of key species which have column densities that are not very sensitive to the rate uncertainties, making them good potential tracers of physical conditions in disks.  We identify about a hundred reactions with the most problematic rate coefficients, which need to be determined more accurately in order to improve the reliability of modern astrochemical models. Second, we build a realistic astrochemical model using a Monte Carlo approach to all chemical processes, which is the   first time this has been done.  This allows us to properly take into account the stochastic nature of grain surface chemical reactions, which are of essential importance for the formation of organic molecules -- i.e., the precursors   of life as we know it. The recent modified rate approach (MRE) of Garrod et al. (2008) is shown to be the most accurate fast approach of   accounting for stochastic effects in astrochemical modeling. Finally, we apply our model to the study of the chemical composition of an evolving protoplanetary disk with grain growth, in order to reveal chemical tracers of this process. For the first time, a state-of-the-art astrochemical model is coupled with a detailed model of grain growth and sedimentation.
date: 2009
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/10161/1/PhD_thesis_Vasyunin.pdf
identifier: DOI:10.11588/heidok.00010161
identifier: urn:nbn:de:bsz:16-opus-101615
identifier:   Vasyunin, Anton  (2009) Chemistry in the ISM and disks on the verge of planet formation.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/10161/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng