Large areas of space are filled by molecular clouds that consist of gas and dust grains that are the remnants of dead stars. When these clouds start collapsing, the decreasing temperature and... Show moreLarge areas of space are filled by molecular clouds that consist of gas and dust grains that are the remnants of dead stars. When these clouds start collapsing, the decreasing temperature and increasing density cause gas particles to start accreting onto dust grain surfaces. This results in layered geometries of partially mixed ices on top of the grains that act as molecule reservoirs and cryogenic catalysts on which both simple and complex molecules form in surface reactions. These grains form the material from which celestial bodies form. A good understanding of the elementary processes taking place in dark interstellar clouds, therefore, is necessary to understand the chemical inventory of stellar systems, like our own Solar system.This thesis focuses on laboratory studies investigating the surface chemistry of CO-rich ices on dust grains at temperatures as low as 10 K. The formation mechanisms of complex organic molecules (COMs) are investigated by non-energetic processes (e.g., hydrogenation) and energetic processes (e.g., photolysis). Moreover, the net transfer of the newly formed hydrogenated species from grain surfaces into the gas phase through non-thermal desorption is investigated to link the detection of COMs in the gas phase to their formation in the solid state. Show less
This thesis focus on the study of the Interstellar Medium (ISM) of the Milky Way and consists of two parts: in the first one we present a study of the dust properties in HII regions and their... Show moreThis thesis focus on the study of the Interstellar Medium (ISM) of the Milky Way and consists of two parts: in the first one we present a study of the dust properties in HII regions and their surrounding PDRs. We focus our studies on two compact HII regions: W3(A) and the Orion Nebula (Chapters 2 and 3, respsectively). Using SOFIA/FORCAST observations, we determine the properties of dust in the ionized gas, their surrounding PhotoDissociation Regions and their parent molecular clouds. One of the most important conclusions of this thesis is that the grain growth can affect the dust size distribution in regions of massive star formation. The large amount of archival data available for Orion allow us to study other important phenomena related to dust in this region, such as the photoelectric heating effect and Lyman alpha heating. The second part of this thesis presents theoretical studies of the properties of the cold neutral medium (CNM) using carbon radio recombination lines (CRRL). Chapters 4 and 5 consists on the complete theory of CRRLs from the level population equation to the radiative transfer equation. Using these models and observations of CRRLs the physical parameters of the CNM can be determined. Show less
