Project Details
Projekt
Beitrag Aktiver Galaxienkerne zur extragalaktischen Neutrinohintergrundstrahlung
Applicant
Dr. Tanja Kneiske
Subject Area
Astrophysics and Astronomy
Term
from 2005 to 2008
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 5450932
The new generation of neutrino telescopes like IceCube will be able to test theoretical predictions for the extragalactic Neutrinobackground based on the assumption that the ultrahigh energy component of the cosmic ray spectrum is produced in extragalactic sources like Active Galactic Nuclei (AGN). Because of the cosmological distance of these sources, information about the direction of cosmic rays are lost due to magnetic fields. Thus, high energy photons or weak interacting particles like neutrinos are needed to learn more about the origin of high and ultrahigh energy cosmic rays.Gamma-ray photons produced in pion decays are directly related to high energy neutrinos. Theoretical models for particle acceleration and interaction in extragalactic sources compared with their observed photon spectra can be used to predict the neutrino output. From a single source spectrum and the observations of diffuse photon backgrounds an upper limit on the extragalactic neutrino background can be derived.In the project so far gamma-ray spectra of blazars, Faranoff Riley Typ I objects (FR-I galaxies) and Luminous Infrared Galaxies (LIGs) have been modeled. Observed luminosity functions for each object class have been extrapolated to lower luminosities and higher redshifts to calculate the contribution to the extragalactic gamma-ray background from each object class. From the contribution of blazars to the GeV gamma-ray background an estimate for a neutrino flux from blazars has been developed. A main point was to include the effect of gamma-ray absorption (at GeV, 109 - TeV 1012 eV energies) in the source spectra due to pair production with ambient low energy photons using a model for the ultraviolet (UV) to infrared (IR) metagalactic radiation field developed by the applicant. The pair production process is followed by a particle cascade producing GeV gamma-ray photons which will also contribute to the gamma-ray background and lower the resulting diffuse neutrino flux.
DFG Programme
Research Fellowships
