Complex Organic Molecules (COMs) have been detected in objects across different stages of stellar evolution. Many of these COMs are expected to form on interstellar ice and transfer later to the... Show moreComplex Organic Molecules (COMs) have been detected in objects across different stages of stellar evolution. Many of these COMs are expected to form on interstellar ice and transfer later to the gas phase. However, due to the challenge of detecting and assigning molecules in interstellar ice observations, the only frozen COM that has been unambiguously identified is methanol. This scenario is about to change, as the exceptional capabilities of the James Webb Space Telescope (JWST) enable the observation of weak signatures of molecules in interstellar ice.This thesis has a main focus on laboratory studies to support interstellar ice observation with the JWST. The results of the spectroscopic characterization of three COMs, acetone, methylamine, and methyl cyanide mixed in interstellar ice analogs are presented in Chapters 3, 4, and 5, respectively. The potential of their absorption features to trace these species in JWST observations is also discussed. Chapter 6 presents a new experimental approach to studying morphological changes in frozen CO, which is important to understand its morphology in space. Chapter 7 presents a computational study that simulates the infrared spectra of small fullerenes (between 44-70 C atoms) and provides insights for future JWST searches for these molecules Show less
Stars like the sun are born in large molecular clouds existing from gas and dust. During the formation process, the chemical composition of the material can be altered drastically by the changing... Show moreStars like the sun are born in large molecular clouds existing from gas and dust. During the formation process, the chemical composition of the material can be altered drastically by the changing physical conditions. This thesis focuses on how molecules in young protostellar systems are inherited from molecular clouds. The emphasis lies on so-called complex organic molecules and accretion shocks.Based on observations of complex organic molecules, it can be suggested that the molecular composition of a protostellar disk is (partially) inherited from the molecular cloud. The abundance ratio between various molecules is remarkably constant in various protostellar systems, implying that they form under similar conditions in molecular clouds. Furthermore, absence of complex molecules in observations does not directly mean that they are absent in the protostellar system but rather that they are hidden from us.This thesis also focuses on accretion shocks at the boundary between infalling cloud and protostellar disk. Based on a comparison between detailed numerical simulations and observations it can be suggested that strong accretions are not always present in protostellar systems. In turn, this suggests that the chemical composition in protostellar disks can be directly inherited from the molecular cloud. Show less
This Thesis shows discoveries in non-linear astrochemical kinetics as well as a deeper analysis of dark clouds chemistry. It is concluded that autocatalysis in interstellar gas-phase chemistry... Show moreThis Thesis shows discoveries in non-linear astrochemical kinetics as well as a deeper analysis of dark clouds chemistry. It is concluded that autocatalysis in interstellar gas-phase chemistry leads to bistability but when coupled with the gas-grain exchange of key species, the system can show Hopf bifurcation and lead to the appearance of complex chemical oscillations. The results and discussion of the five chapters allow further understanding of the chemical evolution in a gas phase system and in a gas-grain environment, providing better predictions to compare with future observations. Show less
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
Organic molecules in interstellar space are important as they influence the structure of galaxies and star formations. Studying catalytic processes in space allows us to understand how molecular... Show moreOrganic molecules in interstellar space are important as they influence the structure of galaxies and star formations. Studying catalytic processes in space allows us to understand how molecular species are formed and chemically evolved in the interstellar medium and solar system objects. Quantum chemical methods, such as “Density Functional Theory” (DFT), can be employed to study the chemical pathways for the formation of molecular species, which is challenging with only observations and experiments. This thesis studies, with DFT methods, how polycyclic aromatic hydrocarbons (PAHs), the most abundant organic species in space, catalyze the formation of molecular hydrogen in the interstellar medium. Specifically, how linear PAHs become superhydrogenated and how the presence of Stone Wales defect in PAHs contributes to their catalytic activity for molecular hydrogen formation. In addition, this thesis reports the study of the catalytic activity of forsterite, a silicate mineral abundant in grains, asteroids, and meteorites. Specifically, the presence of Schottky MgO vacancy in forsterite can catalyze the C-H activation of PAHs as the first step to study the breakdown reaction of PAHs in asteroidal settings. The latter is indispensable to understand the formation of the so-called organic inventory of solar system objects. Show less
The focus of this thesis is how stars like our Sun and planets like Jupiter, Saturn, and Earth are formed. With arrays of radio telescopes, I observed the environments where the first stages of... Show moreThe focus of this thesis is how stars like our Sun and planets like Jupiter, Saturn, and Earth are formed. With arrays of radio telescopes, I observed the environments where the first stages of star and planet formation occur. This thesis focuses on characterizing different components of young protostellar systems, most notably their jets and disks. Using interferometric radio observations with ALMA array, I provided information on key chemical tracers of different components of the protostellar systems. By characterizing the radio signal from young stars with ALMA and VLA interferometers, I was able to disentangle an emission from the jet and the disk. This led to an unexpected development: I was able to compare dust masses of young disks with those of older disks for the first time. By comparing this information with masses of the extrasolar planets detected so far I showed that the solid cores of gas giants must form in the first 0.1 Myr of stellar life. That is an important time constrain, that pushes the onset of planet formation earlier and highlights the importance of characterization of the youngest protostars in understanding the origin of Solar System and Earth. Show less
This thesis focuses on protoplanetary disks: flattened structures of gas and dust around young stars in which planets are expected to form and grow. Physical-chemical models that compute the... Show moreThis thesis focuses on protoplanetary disks: flattened structures of gas and dust around young stars in which planets are expected to form and grow. Physical-chemical models that compute the thermal structure and chemical composition of protoplanetary disks are compared to observations to increase our understanding of the processes that shape these disks.Chapters two and three investigate the sizes of protoplanetary disks in the context of evolution of the dust. A gas disk that is observed to be four times more extended than the dust disk is found to be a clear indication that the dust has drifted inward. Detailed modeling reveals that five out of a sample of 10 disks in the Lupus star-forming region show evidence for dust evolution. Chapter four shows that observed gas outer radii are consistent with disks evolving viscously, assuming disks start out small and evolve slowly. Chapter five reveals that the chemical conversion of CO into more complex species cannot by itself explain the low observed CO isotopolog line fluxes. Finally, Chapter six uses non-detections of the HD emission line to put an upper limit on the total mass of disks and rules out that they are currently gravitationally unstable. Show less
This thesis is largely an experimental study on the formation of solid-state simple and complex organic molecules in the H2O-rich and CO-rich ice phases of dense interstellar clouds and dark cores.... Show moreThis thesis is largely an experimental study on the formation of solid-state simple and complex organic molecules in the H2O-rich and CO-rich ice phases of dense interstellar clouds and dark cores. Astronomical ice observations are also presented and are strongly linked to the experimental work. For decades, it has been realized that particularly complex organic molecules can be formed at extremely low temperatures with the aid of 'energetic' particles, such as UV photons. In this thesis, it is clearly shown that complex organic molecules can also be formed without 'energetic' particles. The experimental laboratory work is supported by computational calculations to constrain which molecules are more or less likely to form under the extreme conditions of interstellar clouds. Show less
To address the fundamental questions of how life on Earth emerged and how common life may be in the Universe, it is crucial to know the chemical composition of the planet-forming material. Planets... Show moreTo address the fundamental questions of how life on Earth emerged and how common life may be in the Universe, it is crucial to know the chemical composition of the planet-forming material. Planets were originally thought to form in protoplanetary disks, but studies of both disks and our Solar System show that planet formation already starts much earlier, in disks that are still embedded in cloud material. These young disks, however, are largely uncharacterised. This thesis presents a number of case studies on the physical and chemical structure of young disks, including the first temperature measurements showing that young disks are too warm for CO ice, unlike protoplanetary disks. In addition, it is shown that young disks around outbursting stars are the ideal sources to probe the the chemical complexity in planet-forming material. Show less
This thesis discusses the physical and chemical processes than influence the composition of forming planets. The focus is on the effect of these processes on the abundance and distribution of... Show moreThis thesis discusses the physical and chemical processes than influence the composition of forming planets. The focus is on the effect of these processes on the abundance and distribution of moleculus in the birth places of planets, proto-planetary disks. The thesis further discusses how current and future observations can be used to quantify the effects of these processes. A good grasp of these processes will enable researchers to link the composition of (exo)planets to their formation origin. Specifically this thesis studies the the most abundant carbon and oxygen carrying molecules, CO, CO2 and H2O. Chemical modelling of CO indicates that conversion of CO into other molecules needs to be fast to explain the current observations. Study of the transport and distribution of CO2 indicate that the measured the CO2 abundance in the surface layers of disks is not bulk CO2 abundance. The power of spectroscopic CO observations in the infrared to find physical structures in disks, possibly created by planets is also discussed. Finally, a combination of infrared observations is used to show that the closest proto-planetary disk is poor in molecules that contain carbon and oxygen, indicating that a process is removing these molecules from the gas phase. Show less
Astronomical observations of cold regions in the universe show a rich inventory of ices. Part of these ices may end up on planets like our own, but in that journey they will be exposed to... Show moreAstronomical observations of cold regions in the universe show a rich inventory of ices. Part of these ices may end up on planets like our own, but in that journey they will be exposed to considerable amounts of radiation. As water is the main component of these ices, the optical and photochemical properties of water ice largely determine how the radiation affects the molecules embedded in the ice. In this thesis, water ice is investigated as a host for photochemical reactions. A new laboratory setup is constructed, and two types of molecules are studied: glycine, an amino acid, and triphenylene, a polycyclic aromatic hydrocarbon. The photochemistry upon exposure to ultraviolet radiation is studied using UVvis and infrared spectroscopy. In addition, the optical properties of water ice are constrained in the UV-vis range, resulting in high-resolution optical constants, relevant for all ice-rich environments - from far away in space to our atmosphere. Water itself does not absorb light in this range, but as most organic molecules do, and are destroyed by radiation in this range, this is of high importance for molecules within the ice. Show less
The thesis explores how interstellar chemistry evolves as a function of time and changing physical architectures during the formation of stars. The motivation behind the work is an aspiration to... Show moreThe thesis explores how interstellar chemistry evolves as a function of time and changing physical architectures during the formation of stars. The motivation behind the work is an aspiration to better understand how the Solar System came to be, which processes led to its chemical composition and ultimately, what enabled life to evolve on Earth. Show less
This thesis examines the link between simple molecules and the underlying structure and chemistry within protoplanetary disks - the birthplaces of planets. The chapters describe the analysis and... Show moreThis thesis examines the link between simple molecules and the underlying structure and chemistry within protoplanetary disks - the birthplaces of planets. The chapters describe the analysis and interpretation of data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) interferometer, primarily in two disks around the young stars HD 163296 and HD 169142. Observations of dust and molecular gas probe the relationship between the dust structure, the gas distribution, and the chemical processes that give rise to the gaseous species. In the disk around HD 169142, substructure in the millimeter dust and carbon monoxide gas strongly suggests the presence of giant planets sweeping up disk material. Meanwhile, molecular ions reveal previously hidden structure in the gas deep within the disk beyond the millimeter dust edge. In the disk around HD 163296, carbon monoxide and the simple organic molecule formaldehyde show radial variation connected to the millimeter dust edge. The organic molecule methanol is not detected in the disk, suggesting differences in the production of formaldehyde and methanol. This thesis concludes that the distribution of simple molecules is connected to the dust size distribution in disks, while more complex molecules remain elusive but can still provide constraints on disk chemistry. Show less
In this thesis, we present new laboratory data of interstellar dust analogues. These measurements, were transformed to interstellar dust models and were used to fit the spectra of low-mass X... Show moreIn this thesis, we present new laboratory data of interstellar dust analogues. These measurements, were transformed to interstellar dust models and were used to fit the spectra of low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. In these spectra, we focus in particular on the Si K-edge. The XAFS features in the Si K-edge offer a range of possibilities to study silicon-bearing dust, such as investigating the crystallinity, abundance and the chemical composition. We also present a study on the prospects of observing carbon, sulfur, and other lower abundance elements (namely Al, Ca, Ti and Ni) present in the interstellar medium using future X-ray instruments. We simulated data of instruments with characteristics of resolution and sensitivity of the Athena, XARM and Arcus concepts. Lastly, we explore the theory of X-ray scattering for a new parameter space where the small angle approach is no longer valid and where the size distribution of the dust includes large (> 1 micron) particles. We apply this theory to the environment of stellar debris disks where such conditions apply. We use as a best test case the debris disk of AU Microscopii. Show less
This thesis addresses the chemical processes that determine the compositions of giant planet atmospheres. Connecting the observed composition of exoplanets to their formation sites often involves... Show moreThis thesis addresses the chemical processes that determine the compositions of giant planet atmospheres. Connecting the observed composition of exoplanets to their formation sites often involves comparing the observed planetary atmospheric carbon-to-oxygen (C/O) ratio to a disk midplane model with a fixed chemical composition. In this scenario chemistry during the planet formation era is not considered, and the C/O ratios of gas and ice in disk midplane are simply defined by volatile icelines in a midplane of fixed chemical composition. However, kinetic chemical evolution during the lifetime of the gaseous disk can change the relative abundances of volatile species, thus altering the C/O ratios of planetary building blocks. In my chemical evolution models I utilize a large network of gas-phase, grain-surface and gas-grain interaction reactions, thus providing a comprehensive treatment of chemistry. In my talk I will show how chemical evolution can modify disk miplane chemistry and how this affects the C/O ratio of giant planet-forming material. I will argue that midplane chemical evolution needs to be addressed when predicting the chemical makeup of planets and their atmospheres. And as an extra, I will propose that chemical evolution can help constrain the formation histories of comets. Show less
This thesis is about the study of hydrocarbons via infrared spectroscopy. Hydrocarbons play an important role in the chemistry of a variety of astronomical environments from the diffuse... Show moreThis thesis is about the study of hydrocarbons via infrared spectroscopy. Hydrocarbons play an important role in the chemistry of a variety of astronomical environments from the diffuse interstellar medium to dense hydrocarbon atmospheres of solar system bodies (e.g., planetary atmospheres of Jupiter and Saturn’s moon Titan) and exoplanets. For most astronomical objects, the determination of chemical abundances, and consequently an understanding of the chemical evolution relies upon the observation of molecular spectra. However, to date astronomical models need to make assumptions, because not all of the molecules expected have been observed. This is due, in part, to a lack of accurate spectral data, which is needed for unambiguous identification. Using a combination of high-resolution infrared experiments and/or high level ab initio calculations of vibration frequencies and ground state spectroscopic constants, the infrared spectral data of HC2H, HC4H, HC6H, HC8H, C3H4, c-C3H3+ and Dn-PAHs (polycyclic aromatic hydrocarbons, PAH) are studied and presented, in order to fill in some of the missing spectral data. Show less
My work focuses on a class of astronomical objects called protoplanetary disks. These flattened structures rotating around young stars are made of gas and dust and are the places where planets,... Show moreMy work focuses on a class of astronomical objects called protoplanetary disks. These flattened structures rotating around young stars are made of gas and dust and are the places where planets, like our own Earth, are formed. One of the main properties needed to explain the process of planet formation is the mass of protoplanetary disks. There is however not yet a consensus on how such masses can be reliably measured from disk observations. In this thesis, I investigate weather less abundant isotopologues of carbon monoxide (CO) are good candidates for tracing disk masses. Initially I tackle the problem from a theoretical point of view by running a grid of physical-chemical disk models. Subsequently I compare my model predictions with recently acquired observations of protoplanetary disks in the Lupus star-forming region. The conclusion of my work is that CO isotopologues are good disk mass tracers, but they need to be calibrated. Observations of other molecules like hydrogen deuteride (HD), atomic carbon and hydrocarbons can serve this cause. Show less
Planets are formed in disks of gas and dust around young stars. These planet-forming disks undergo several physical and chemical processes that can lead to planetary systems like our own. This... Show morePlanets are formed in disks of gas and dust around young stars. These planet-forming disks undergo several physical and chemical processes that can lead to planetary systems like our own. This thesis uses data of two well known planet-forming disks around TW Hya and HD 163296 taken with the Atacama Large (sub)Milimeter Array (ALMA) and the Herschel Space Telescope to study the spatial distribution of their dust and gas content. In particular, we aim to constrain the spatial distribution of the main oxygen- and nitrogen-bearing species in planet-forming disks and to explore the relationship between their physical features and the formation and chemistry of common molecular species. By analysing water and ammonia emission form the disk around TW Hya, we conclude that the location of oxygen- and nitrogen-bearing volatiles in planet-forming disks are set by grain evolution, in particular radial drift. In addition, we conclude that the spatial location of temperature-sensitive species trace substructures in the temperature profile of protoplanetary disks and therefore (indirectly) the impact of dust evolution process on its morphology. Show less
In this thesis chemical and physical processes in the ice mantles on interstellar dust grains are studied. With the Atacama Large Millimetre/submillimetre Array molecules of interest to the... Show moreIn this thesis chemical and physical processes in the ice mantles on interstellar dust grains are studied. With the Atacama Large Millimetre/submillimetre Array molecules of interest to the formation of bigger, life-bearing molecules are detected for the first time around the sun-like low-mass protostar IRAS 16293-2422. These detections give clues about the earliest conditions our solar system formed under and potentially how life on earth emerged. Laboratory studies investigate the formation of these complex species in a laboratory set-up mimicking the conditions on interstellar icy dust grains. In this ways formation routes for molecules with a so-called amide functional group are mapped. Show less
Multiple stars, that is two or more stars composing a gravitationally bound system, are common in the universe.They are the cause of many interesting phenomena, from supernovae and planetary... Show moreMultiple stars, that is two or more stars composing a gravitationally bound system, are common in the universe.They are the cause of many interesting phenomena, from supernovae and planetary nebulae, to binary black hole mergers. Observations of main sequence stars, young stars and forming protostars show that multiplicity is common, and that multiple stars are born. This thesis focuses on several of the open questions on the formation and evolution of multiple stars, namely when do rotationally supported disks form, the factors leading to fragmentation of the cloud core and the physico-chemical structure of multiple protostars. For this purpose, radio interferometric observations of dust continuum and molecular line emission, coupled with chemical and physical models are used to study several young, deeply embedded prototstars. The results of this thesis contribute useful pieces to the puzzle of multiple star formation, demonstrating that rotationally supported disks can form early in the star formation process, while temperature and the presence of disks can alter the physico-chemical protostellar structure. Furthermore, the results of this thesis indicate that mass, rather than temperature, could be an important factor in fragmentation of cloud cores, and the formation of multiple stars. Show less