Implications of cosmological gamma-ray absorption

Free access article

Issue		A&A Volume 386, Number 1, April IV 2002


Page(s)		1 - 11
Section		Cosmology
DOI		http://dx.doi.org/10.1051/0004-6361:20020211

A&A 386, 1-11 (2002)
DOI: 10.1051/0004-6361:20020211

I. Evolution of the metagalactic radiation field

T. M. Kneiske¹, K. Mannheim¹ and D. H. Hartmann²

¹ Universität Würzburg, Am Hubland, 97057 Würzburg, Germany
² Clemson University, Clemson, SC 29634-0978, USA

(Received 9 July 2001 / Accepted 30 January 2002 )

Abstract
Gamma-ray absorption due to $\gamma\gamma$ -pair creation on cosmological scales depends on the line-of-sight integral of the evolving density of low-energy photons in the Universe, i.e. on the history of the diffuse, isotropic radiation field. Here we present and discuss a semi-empirical model for this metagalactic radiation field based on stellar light produced and reprocessed in evolving galaxies. With a minimum of parameters and assumptions, the present-day background intensity is obtained from the far-IR to the ultraviolet band. Predicted model intensities are independent of cosmological parameters, since we require that the comoving emissivity, as a function of redshift, agrees with observed values obtained from deep galaxy surveys. The far-infrared background at present predicted from optical galaxy surveys falls short in explaining the observed one, and we show that this deficit can be removed by taking into account (ultra)luminous infrared galaxies with a seperate star formation rate. The accuracy and reliability of the model, out to redshifts of $z\sim 5$ , allow a realistic estimate of the attenuation length of GeV-to-TeV gamma-rays and its uncertainty, which will be the focus of a subsequent paper.

Key words: galaxies: evolution -- ISM: general -- radiation mechanisms: general -- cosmology: observations

Offprint request: T. M. Kneiske, kneiske@astro.uni-wuerzburg.de

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.