2004/03/12 by Tijana Prodanovic, Tijana Prodanović, Brian D. Fields · 3 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #Particle physics theoretical and experimental studies #astro-ph
paper · pdf · doi:10.1016/j.astropartphys.2004.04.006
published as Astropart.Phys. 21 (2004) 627-635 · 14 pages, 4 figures, AASTeX. Comments welcome
arxiv created 2004/03/12 · openalex publication_date 2004/05/30 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Diffuse gamma rays probe the highest-energy processes at the largest scales. Here we derive model-independent constraints on the hadronic contribution to the Galactic and extragalactic gamma-ray spectra in the energy range 50 MeV < Egamma < 10 GeV. The hadronic component is dominated by emission from neutral pions, with a characteristic spectrum symmetric about mpi0/2. We exploit the well-defined properties of the pion decay spectrum to quantify the maximum pionic fraction of the observed gamma-ray intensity. We find that the Galactic spectrum above 30 MeV can be at most about 50% pionic. The maximum pionic contribution to the extragalactic spectrum is energy dependent; it also depends on the redshift range over which the sources are distributed, ranging from as low as about 20% for pions generated very recently, to as much as 90% if the pions are generated around redshift 10. The implications of these constraints for models of gamma-ray and neutrino emission are briefly discussed.