Corrected Table for the Parametric Coefficients for the Optical Depth of the Universe to Gamma-rays at Various Redshifts

Table 1 in our paper, ApJ 648, 774 (2006) entitled "Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High Energy Gamma-Rays" had erroneous numbers for the coefficients fitting the parametric form for the optical depth of the universe to gamma-rays. The correct values for these parameters as described in the original text are given here in a corrected table for various redshifts for the baseline model (upper row) and fast evolution (lower row) for each individual redshift. The parametric approximation is good for optical depths between 0.01 and 100 and for gamma-ray energies up to ~2 TeV for all redshifts but also for energies up to ~10 TeV for redshifts less than 1.Comment: Table 1 corrected and new gamma-ray energy range of validity give

Erratum: Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High Energy Gamma-Rays

Table 1 in our paper had erroneous numbers for the coefficients fitting the parametric form for the optical depth of the universe to gamma-rays; tau. The correct values for these parameters as described in the original text are given in the table for various redshifts for the baseline model (upper row) and fast evolution (lower row) for each individual redshift

Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for 0<z<60 < z < 6 and the Optical Depth of the Universe to High Energy Gamma-Rays

We calculate the intergalactic photon density as a function of both energy and redshift for 0 < z < 6 for photon energies from .003 eV to the Lyman limit cutoff at 13.6 eV in a Lambda-CDM universe with $\Omega_{\Lambda} = 0.7$ and $\Omega_{m} = 0.3$. Our galaxy evolution model gives results which are consistent with Spitzer deep number counts and the spectral energy distribution of the extragalactic background radiation. We use our photon density results to extend previous work on the absorption of high energy gamma-rays in intergalactic space owing to interactions with low energy photons and the 2.7 K cosmic background radiation. We calculate the optical depth of the universe, tau, for gamma-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from ~0 to 5. We also give an analytic fit with numerical coefficients for approximating $\tau(E_{\gamma}, z)$. As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z = 0.117 and compare it with the spectrum observed by the H.E.S.S. air Cherenkov gamma-ray telescope array.Comment: final version to be published in Ap

Cosmic Physics: The High Energy Frontier

Cosmic rays have been observed up to energies $10^8$ times larger than those of the best particle accelerators. Studies of astrophysical particles (hadrons, neutrinos and photons) at their highest observed energies have implications for fundamental physics as well as astrophysics. Thus, the cosmic high energy frontier is the nexus to new particle physics. This overview discusses recent advances being made in the physics and astrophysics of cosmic rays and cosmic gamma-rays at the highest observed energies as well as the related physics and astrophysics of very high energy cosmic neutrinos. These topics touch on questions of grand unification, violation of Lorentz invariance, as well as Planck scale physics and quantum gravity.Comment: Topical Review Paper to be published in the Journal of Physics G, 50 page

The Signature of Large Scale Structures on the Very High Energy Gamma-Ray Sky

If the diffuse extragalactic gamma ray emission traces the large scale structures of the universe, peculiar anisotropy patterns are expected in the gamma ray sky. In particular, because of the cutoff distance introduced by the absorption of 0.1-10 TeV photons on the infrared/optical background, prominent correlations with the local structures within a range of few hundreds Mpc should be present. We provide detailed predictions of the signal based on the PSCz map of the local universe. We also use mock N-body catalogues complemented with the halo model of structures to study some statistical features of the expected signatures. The results are largely independent from cosmological details, and depend mostly on the index of correlation (or bias) of the sources with respect to the large scale distribution of galaxies. For instance, the predicted signal in the case of a quadratic correlation (as it may happen for a dark matter annihilation contribution to the diffuse gamma flux) differs substantially from a linear correlation case, providing a complementary tool to unveil the nature of the sources of the diffuse gamma ray emission. The chances of the present and future space and ground based observatories to measure these features are discussed.Comment: 26 pages, 9 figures; matches published versio