Semi-analytic modeling of the EBL and consequences for extragalactic
  gamma-ray spectra
  Attenuation of high-energy gamma rays by pair-production with UV, optical and
IR extragalactic background light (EBL) photons provides a link between the
history of galaxy formation and high-energy astrophysics. We present results
from our latest semi-analytic models (SAMs), which employ the main ingredients
thought to be important to galaxy formation and evolution, as well as an
improved model for reprocessing of starlight by dust to mid- and far-IR
wavelengths. These SAMs are based upon a Lambda-CDM hierarchical structural
formation scenario, and are successful in reproducing a large variety of
observational constraints such as number counts, luminosity and mass functions,
and color bimodality. Our fiducial model is based upon a WMAP5 cosmology, and
treats dust emission using empirical templates. This model predicts a
background flux considerably lower than optical and near-IR measurements that
rely on subtraction of zodiacal and galactic foregrounds, and near the lower
bounds set by number counts of resolvable sources at a large number of
wavelengths. We also show the results of varying cosmological parameters and
dust attenuation model used in our SAM. For each EBL prediction, we show how
the optical depth due to electron-positron pair-production is affected by
redshift and gamma-ray energy, and the effect of gamma-ray absorption on the
spectra of a variety of extragalactic sources. We conclude with a discussion of
the implications of our work, comparisons to other models and key measurements
of the EBL and a discussion of how the burgeoning science of gamma-ray
astronomy will continue to help constrain cosmology. The low EBL flux predicted
by our fiducial model suggests an optimistic future for further studies of
distant gamma-ray sources.
