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Identifier

000401565

Title

Gamma-Rays from the high-redshift universe

Alternative Title

Ακτινοβολία-γ από περιοχές του σύμπαντος με υψηλή ερυθρόπηση

Author

Κόμης, Ιωάννης Γ.

Thesis advisor

Παυλίδου, Βασιλική

Reviewer

Ζέζας, Ανδρέας

Abstract

The present thesis is a study of gamma-rays from the high-redshift Universe. In particular, we examine normal star-forming galaxies as one of the main components of the extragalactic gamma- ray background (EGRB). Despite the new data from the Fermi Gamma-Ray Space Telescope that have been collected through the eight years of operation, the contribution of normal star-forming galaxies to the extragalactic gamma-ray background (EGRB) remains poorly constrained. In this work, we present a comprehensive analysis of factors that can affect estimates of the EGRB: a) possible sources of redshift dependence of the gamma-ray emissivity of a typical galaxy including evolving metallicity, b) cosmic star-formation history and c) the slope of the scaling between star formation tracers and gamma-ray luminosity. Since the number of resolved galaxies is small (8 galaxies), we explicitly test the effect of small number statistics to the empirical slope of this scaling. We conclude that the results are sensitive to the number of resolved galaxies, and we place upper and lower limits to the potential contribution of star forming galaxies to the EGRB for energies between 100 MeV and 100 GeV.

Language

English

Subject

Analytical galaxies

Diffuse background

Galaxies

Luminosity function

Mass function

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