The Cosmological Evolution of Blazars and the Extragalactic Gamma-Ray
  Background in the Fermi Era
  The latest determination of the extragalactic gamma-ray background (EGRB)
radiation by Fermi is compared with the theoretical prediction of the blazar
component by Inoue & Totani (2009; hereafter IT09). The Fermi EGRB spectrum is
in excellent agreement with IT09, indicating that blazars are the dominant
component of the EGRB, and contributions from any other sources (e.g., dark
matter annihilations) are minor. It also indicates that the blazar SED
(spectral energy distribution) sequence taken into account in IT09 is a valid
description of mean blazar SEDs. The possible contribution of MeV blazars to
the EGRB in the MeV band is also discussed. In five total years of
observations, we predict that Fermi will detect ~1200 blazars all sky down to
the corresponding sensitivity limit. We also address the detectability of the
highest-redshift blazars. Updating our model with regard to high-redshift
evolution based on SDSS quasar data, we show that Fermi may find some blazars
up to z~6 during the five-year survey. Such blazars could provide a new probe
of early star and galaxy formation through GeV spectral attenuation signatures
induced by high-redshift UV background radiation.
