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Bridging the gap between physics and chemistry in early stages of star formation

A dense region of a gaseous and dusty cloud collapses to form a protostar surrounded by a disk and an envelope. This thesis uses both observations and models to study physical and chemical conditions of these protostellar systems which are likely where planets start to form.

P. Nazari
13 February 2024
Thesis in Leiden Repository

From the observational side, ALMA is used to quantify abundance ratios of complex organic molecules (COMs) in the gas around young protostars. These ratios are found to be remarkably constant for various nitrogen-bearing COMs which points to formation of these molecules under similar conditions, likely in ices of the prestellar phase. Moreover, observations of JWST are used to tentatively detect molecules such as methyl cyanide and ethyl cyanide in interstellar ices for the first time. In addition, high angular resolution ALMA observations of a protostellar system are analyzed to report the first detection of a disk wind candidate in methanol and hydrogen cyanide. From the modeling side, radiative transfer models are used to investigate how physical conditions such as source structure can change the molecular emission and molecular abundances. These models show that disk and optically thick dust can decrease the emission from COMs and change the correlations among their column densities.

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