Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0807.4246

Photon propagation and the VHE gamma-ray spectra of blazars: how transparent is really the Universe?

A. De Angelis·O. Mansutti·M. Persic·M. Roncadelli
View original source ↗Read source document ↗Export metadata ↓

Abstract

Recent findings by gamma-ray Cherenkov telescopes suggest a higher transparency of the Universe to very-high-energy (VHE) photons than expected from current models of the Extragalactic Background Light. It has been shown that such transparency can be naturally explained by the DARMA scenario, in which the photon mixes with a new, very light, axion-like particle predicted by many extensions of the Standard Model of elementary particles. We discuss the implications of DARMA for the VHE gamma-ray spectra of blazars, and show that it successfully accounts for the observed correlation between spectral slope and redshift by adopting for far-away sources the same emission spectrum characteristic of nearby ones. DARMA also predicts the observed blazar spectral index to become asymptotically independent of redshift for far-away sources. Our prediction can be tested with the satellite-borne Fermi/LAT detector as well as with the ground-based Cherenkov telescopes HESS, MAGIC, CANGAROOIII, VERITAS and the Extensive Air Shower arrays ARGO-YBJ and MILAGRO.

Explore related subjects

astro-phhep-ph

Keep this discovery

BibTeXRIS

A. De Angelis, O. Mansutti, M. Persic, M. Roncadelli. 2008-11-23. Photon propagation and the VHE gamma-ray spectra of blazars: how transparent is really the Universe?. https://doi.org/10.1111/j.1745-3933.2008.00602.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2016

Distribution functions for a family of axially symmetric galaxy models

We present the derivation of distribution functions for the first four members of a family of disks, previously obtained in (MNRAS, 371, 1873, 2006), which represent a family of axially symmetric galaxy models with finite radius and well behaved surface mass density. In order to do this we employ several approaches that have been developed starting from the potential-density pair and, essentially using the method introduced by Kalnajs (Ap. J., 205, 751, 1976) we obtain some distribution functions that depend on the Jacobi integral. Now, as this method demands that the mass density can be properly expressed as a function of the gravitational potential, we can do this only for the first four discs of the family. We also find another kind of distribution functions by starting with the even part of the previous distribution functions and using the maximum entropy principle in order to find the odd part and so a new distribution function, as it was pointed out by Dejonghe (Phys. Rep., 133, 217, 1986). The result is a wide variety of equilibrium states corresponding to several self-consistent finite flat galaxy models.

astro-ph↗
arXiv2016

Cosmic-Ray Nuclei, Antiprotons and Gamma-rays in the Galaxy: a New Diffusion Model

We model the transport of cosmic ray nuclei in the Galaxy by means of a new numerical code. Differently from previous numerical models we account for a generic spatial distribution of the diffusion coefficient. We found that in the case of radially uniform diffusion, the main secondary/primary ratios (B/C, N/O and sub-Fe/Fe) and the modulated antiproton spectrum match consistently the available observations. Convection and re-acceleration do not seem to be required in the energy range we consider: $1 < E < 10^3$ GeV/nucleon. We generalize these results accounting for radial dependence of the diffusion coefficient, which is assumed to trace that of the cosmic ray sources. While this does not affect the prediction of secondary/primary ratios, the simulated longitude profile of the diffuse $γ$-ray emission is significantly different from the uniform case and may agree with EGRET measurements without invoking ad hoc assumptions on the galactic gas density distribution.

astro-ph↗
arXiv2016

Black Stars and Gamma Ray Bursts

Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed "black stars". Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

astro-ph↗