This thesis focus on the interaction between M dwarf stellar winds and Galactic cosmic rays and the possible effects on the habitability of exoplanets. We use numerical simulations to describe the... Show moreThis thesis focus on the interaction between M dwarf stellar winds and Galactic cosmic rays and the possible effects on the habitability of exoplanets. We use numerical simulations to describe the stellar winds of M dwarfs using observable constraints, such as the mass-loss rate, X-ray luminosity, and magnetic field strength/flux. Additionally, we use numerical simulations to describe the propagation of Galactic cosmic rays within M dwarf planetary systems. With these simulations, we can calculate the flux of Galactic cosmic rays reaching exoplanet magnetospheres/atmospheres. Measuring cosmic ray fluxes in exoplanet atmospheres is yet not possible, but cosmic rays are an important ingredient in the context of planetary habitability. For this reason, quantifying these fluxes is essential to complete the habitability “puzzle”. Future exoplanet atmosphere observations with space telescopes, such as the JWST and the ARIEL, will enable us to constrain cosmic ray fluxes in exoplanet atmospheres. Show less
Zhou, P.; Zhang, G.-Y.; Zhou, X.; Arias de Saaverda Benitez, M.; Koo, B.C.; Vink, J.; ... ; Lee, Y.H. 2022
This thesis revolves around the electronic spectroscopy of molecules in the laboratory and the search for the carriers of the diffuse interstellar bands (DIBs). The electronic spectra of carbon... Show moreThis thesis revolves around the electronic spectroscopy of molecules in the laboratory and the search for the carriers of the diffuse interstellar bands (DIBs). The electronic spectra of carbon chains are measured and analyzed in the lab, and the abundance of molecules in the diffuse interstellar regions of our Galaxy is quantified to provide some insight on the nature of the DIB carriers and of the environments where they might be found. In particular, cavity-enhanced absorption methods are employed to record spectra of linear hydrocarbons with which molecular constants are obtained. The wavelength positions of the electronic bands found in the lab are then compared to DIB spectra. Finally, absorption lines of interstellar OH+ are searched for in the near-UV spectra of starlight through diffuse and translucent clouds. These lines are used in deriving the abundance of OH+ and inferring the cosmic-ray ionization rates in these interstellar regions. These rates, in turn, are relevant to link to potential DIB carriers in these environments. Show less
Polycyclic Aromatic Hydrocarbons (PAHs) are one of the most common chemical compounds on Earth. These big molecules are naturally present in crude oil and coal deposits, and are also formed by... Show morePolycyclic Aromatic Hydrocarbons (PAHs) are one of the most common chemical compounds on Earth. These big molecules are naturally present in crude oil and coal deposits, and are also formed by incomplete combustion of carbon-containing fuels, hence they are found in car exhaust, cigarette smoke and (too) well-cooked meats. This makes PAHs one of the most widespread organic pollutants. In space, PAHs are an important and ubiquitous component of the Interstellar Medium, dominating the mid-infrared emission of many astronomical objects. However, very little is known about the destiny of PAHs when they are bombarded by high-velocity ions and electrons arising from interstellar shocks, hot gas and cosmic rays (CRs). The research described in this thesis shows that in shocks with velocities above 100 km/s and in a million-degree gas, PAHs are completely destroyed by collisions with electrons, and can survive only if isolated in denser clouds. Destruction by CRs is due to collisions with ions. Because of their high energy (5 MeV - 10 GeV) CRs can access these denser clouds and will set the lifetime of those protected PAHs, which can be used as a __dye__ for tracing the presence of material entrained in the hot gas. Show less
