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Title: Spectra of high-energy neutrinos and AGN population evolution inferred by X-ray/γ-ray surveys
Author: Jacobsen, I. B.
ISNI:       0000 0004 8502 4860
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2015
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In this thesis I investigate the evolution of high-energy neutrinos, and their ability to diagnose the environment of their origin. AGN are identified as candidates for high-energy neutrino production, and the radio-loud population is particularly attractive due to observed energetic regions in the jet features. I derive source populations at different redshifts and brightness using data obtained from AGN surveys detecting X-ray and γ-ray bright sources. These trace the accretion disc and beamed jet luminosities, respectively, and reflect AGN populations varying in observable properties. Two hadronic interaction models are considered to determine neutrino production efficiencies in AGN. The region of high-energy particle production is located at the base of the AGN jet, where relevant interactions are expected to occur. The diffuse neutrino emission on Earth is calculated as the sum of the contributions from various cosmological epochs, and X-ray luminosities. I find that the bulk of AGN sources would produce a neutrino flux far exceeding the current upper limits set on the received neutrino emission. The only neutrino energy spectra consistent with these limits are due to neutrino production in blazars. Additionally, the importance of a reliable luminosity scaling model is demonstrated, and hence the need for an improved understanding of the radiative processes in jets. To further investigate the physical processes relevant to neutrino production, I construct a neutrino luminosity function for blazar sources. The expected neutrino energy distribution is produced by assuming typical parameters, such as luminosity and Lorentz factor, for each class along the blazar sequence. This will establish constraints on possible AGN sources, the relative neutrino duty cycle, and production efficiencies across the sequence.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available