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
A guaranteed source of neutrinos is the production in cosmic ray interactions with the interstellar matter in our Galaxy. The signal has never been detected however and only an upper limit on this... Show moreA guaranteed source of neutrinos is the production in cosmic ray interactions with the interstellar matter in our Galaxy. The signal has never been detected however and only an upper limit on this flux of neutrinos has been published by the AMANDA-II detector. The ANTARES neutrino telescope, located in the Mediterranean Sea, offers a high visibility of the central region of the Milky Way, from where the highest signal is expected. ANTARES data from 2007-2012 were used to compare the flux from a region extending 39 degrees in Galactic longitude and 4.5 degrees in Galactic latitude on either side of the Galactic centre, with the flux from multiple equivalent off-source regions. No significant excess has been observed, and upper limits have been placed on the neutrino flux. The flux limits produced with ANTARES are more than a factor of 10 above the model predictions, which means that a bigger neutrino telescope is needed to constrain the models further. The future KM3NeT telescope is well suited to perform this measurement. Simulations show that by using all neutrinos flavours, KM3NeT should be able to seriously constrain the neutrino flux after about 3 years of operation. Show less
A time integrated search for cosmic neutrinos is discussed in this thesis using four years of data collected by the ANTARES experiment. No statistically significant signal was found, therefore... Show moreA time integrated search for cosmic neutrinos is discussed in this thesis using four years of data collected by the ANTARES experiment. No statistically significant signal was found, therefore upper limits on the neutrino flux were derived. Limits for specific models of RX J1713.7-3946, Vela X and Crab Nebula which include information on the source morphology and spectrum, are also given. 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
