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... Show moreA 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. 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. Show less
The importance of ice in the interstellar medium is indisputable. Gas phase reactions relying on three-body collisions are exceedingly rare in the sparse medium between the stars. On solid surfaces... Show moreThe importance of ice in the interstellar medium is indisputable. Gas phase reactions relying on three-body collisions are exceedingly rare in the sparse medium between the stars. On solid surfaces, atoms and molecules can reside and rove the surface until a reaction takes place. Upon reaction, the released energy is dissipated into the grain, allowing the new species to form. Solid surfaces thus act as sites for chemical processes, that would otherwise be very slow, or not take place at all. This thesis is dedicated to the study of the composition and physical characteristics of interstellar ices using a variety of experimental observational techniques. The overall goal is to shed light on the processes that chemically enrich planet-forming regions. The specific objectives are to characterize morphological changes and molecular composition in interstellar ices, to explore new experimental techniques to study solid state reactions, and to use complex molecules to probe large scale astronomical phenomena. Show less
It has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment as the interstellar medium. In recent years it has become clear that solid... Show moreIt has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment as the interstellar medium. In recent years it has become clear that solid state reactions on icy grains play an important role in the formation of both simple and rather complex molecules. Laboratory based experiments that simulate the UV processing or the impact of H-atoms on interstellar ice analogues are needed in order to investigate the underlying processes. This is the topic of this PhD thesis that mainly summarizes research on SURFRESIDE, one of the ultra-high vacuum setup in the Sackler Laboratory for Astrophysics. It is shown how under fully controlled conditions molecules form when CO and O2 containing ices are bombarded by hydrogen atoms. Surface reaction schemes for methanol, water, carbon dioxide and formic acid formation at low temperatures in space are presented, and it is discussed how species may be chemically linked in space. Show less
