Speaker
Giulia Vannoni
(Max-Planck-Institut für Kernphysik, Heidelberg)
Description
Clusters of galaxies are believed to be able to accelerate Cosmic Rays to ultrahigh energies (~10^18 eV and beyond) at accretion shocks. At this energies, the energy losses induced by the interaction with the CMB
radiation become effective and determine the maximum energy of protons and the shape of the cutoff in the proton energy spectrum. In particular, the dominant energy loss channel becomes pair production.
We present a time dependent numerical calculation of the shock acceleration process where we include self-consistently the presence of energy losses. We accurately calculate the spectra of the produced electron-positron pairs and the X-ray and gamma-ray emission they produce via synchrotron and inverse Compton scattering processes respectively. We find that the radiation spectra show a cutoff harder than exponential and that the downstream and upstream regions contribute almost at the same level to the emission. For the typical characteristics of galaxy clusters, the synchrotron and IC peaks of the electron broadband emission are at comparable levels. The expected emission in gamma-rays is at the limit of
the sensitivity of present generation instruments, however it may be detectable with the future generation of detectors.
Author
Giulia Vannoni
(Max-Planck-Institut für Kernphysik, Heidelberg)
Co-authors
Felix Aharonian
(Dublin Institute for Advanced Studies, Dublin)
Stefano Gabici
(Dublin Institute for Advanced Studies, Dublin)
