We have conducted a full spectral line survey of the 3-13 micron region of two massive protostars, AFGL 2591 and AFGL 2136, for the first time at high spectral resolution. Utilising SOFIA/EXES... Show moreWe have conducted a full spectral line survey of the 3-13 micron region of two massive protostars, AFGL 2591 and AFGL 2136, for the first time at high spectral resolution. Utilising SOFIA/EXES observations, combined with ground based observations from TEXES and iSHELL, many transitions of HCN, C2H2, NH3, CS, CO and H2O are observed, with all species observed to be in absorption. High temperatures (600 K) and abundances (1-10e-6 w.r.t H) of each species are derived. In this thesis, I will present the new insights into the physical conditions and chemical composition of the disks that these absorption lines probe. In particular, hundreds of ro-vibrational transitions of H2O are detected with EXES towards each object, and are linked to a disk wind in AFGL 2591. Column density variations of HCN and C2H2 in bands that probe the same lower level, across different wavelengths, are also discussed, supporting the location of this gas in the circumstellar disk of these protostars. Finally emission lines of HCN are discussed towards MonR2 IRS 3 and are consistent with an origin in a circumstellar disk, or also possibly an expanding shell of gas, supported by P-Cygni profiles of CO lines. 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
Chemistry plays an important role in the study of the physics and evolution of the warm dense Interstellar Medium (ISM). This is found in very different environment, e.g. in the disks around low... Show moreChemistry plays an important role in the study of the physics and evolution of the warm dense Interstellar Medium (ISM). This is found in very different environment, e.g. in the disks around low-mass young stellar objects (YSOs), in the envelopes of massive-YSOs, and in the nuclei of Ultra Luminous Infrared Galaxies (ULIRGS). The excitation temperatures and abundances of the observed molecules provide the observer with a physicochemical snapshot of the regions. The abundances of the molecules depend strongly on temperature, density, radiation field (UV, Infrared, and X-ray) and initial composition of the gas. Infrared spectroscopy is instrumental in the study of dense ISM as many species have transitions in the infrared. Space based instruments, unhindered by the earth atmosphere, allow us to study these. The absorption and emission features are often weak. Therefore a major challenge in using these instruments is to understand the instrumental characteristics and translating that knowledge into usable reduction algorithms. Most of the data used in this thesis are obtained with space based spectrographs, ISO-SWS and Spitzer-IRS, pushing them to their limits. Show less
