Extragalactic gamma-ray background from AGN winds and star-forming
  galaxies in cosmological galaxy formation models
  We derive the contribution to the extragalactic gamma-ray background (EGB)
from AGN winds and star-forming galaxies by including a physical model for the
gamma-ray emission produced by relativistic protons accelerated by AGN-driven
and supernova-driven shocks into a state-of-the-art semi-analytic model of
galaxy formation. This is based on galaxy interactions as triggers of AGN
accretion and starburst activity and on expanding blast wave as the mechanism
to communicate outwards the energy injected into the interstellar medium by the
active nucleus. We compare the model predictions with the latest measurement of
the EGB spectrum performed by the Fermi-LAT in the range between 100 MeV and
820 GeV. We find that AGN winds can provide ~35$\pm$15% of the observed EGB in
the energy interval E_{\gamma}=0.1-1 GeV, for ~73$\pm$15% at E_{\gamma}=1-10
GeV, and for ~60$\pm$20% at E_{\gamma}>10 GeV. The AGN wind contribution to the
EGB is predicted to be larger by a factor of 3-5 than that provided by
star-forming galaxies (quiescent plus starburst) in the hierarchical clustering
scenario. The cumulative gamma-ray emission from AGN winds and blazars can
account for the amplitude and spectral shape of the EGB, assuming the standard
acceleration theory, and AGN wind parameters that agree with observations. We
also compare the model prediction for the cumulative neutrino background from
AGN winds with the most recent IceCube data. We find that for AGN winds with
accelerated proton spectral index p=2.2-2.3, and taking into account internal
absorption of gamma-rays, the Fermi-LAT and IceCube data could be reproduced
simultaneously.
