Fermi-LAT analysis of extended supernova remnants with the new pass 8 data
Abstract
Supernova remnants (SNRs) are nowadays considered as the favoured sources of galactic cosmic rays. When accelerated protons encounter the interstellar material they produce neutral pions, which in turn decay into gamma rays. The observation of the g-ray emission from SNRs therefore is a compelling way to identificate and locate the acceleration sites of the protons. Spatial extension of g-ray sources is an important characteristic for correctly associating their g emission with their counterparts at other wavelengths and for obtaining an unbiased model of their spectra. The purpose of the analyses performed in this thesis is the test of the new Fermi Pass 8 data for the study of the emission of extended sources. The paradigmatic example of W44, one of the brightest extended sources in the g-ray sky, was chosen as case of study. This thesis is structured in four chapters:
Chapter 1 provides an overview of the Fermi-LAT technical characteristics and of the process of selection of the data that are then available for the analysis. Attention is focused on the new event types (based on the quality of the reconstructed energy and direction) that comes with the Pass 8 release. Chapter 2 describes the Fermi Science Tools, the standard instrument for the data analysis in the Fermi-LAT collaboration. The steps followed in a standard likelihood analysis are also presented. Chapter 3 resumes the literature on W44, pointing out the features of the spectral and spatial models used for describing its g-ray emission. Chapter 4 finally presents the results obtained with Pass 8 data analysis on W44 SNR.- Publication:
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Ph.D. Thesis
- Pub Date:
- December 2015
- Bibcode:
- 2015PhDT.......142N