Finke 2009 Modeling the Extragalactic Background Light from Stars and Dust

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说20GeV以下的光子在宇宙中是透明的

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Title:		Modeling the Extragalactic Background Light from Stars and Dust
Authors:		Finke, Justin D.; Razzaque, Soebur; Dermer, Charles D.
Publication:		eprint arXiv:0905.1115
Publication Date:		05/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		12 pages, 9 figures, 3 tables, emulateapj. Submitted to ApJ
Bibliographic Code:		2009arXiv0905.1115F

Abstract

The extragalactic background light (EBL) from the far infrared through the visible and extending into the ultraviolet is thought to be dominated by starlight, either through direct emission or through absorption and reradiation by dust. This is the most important energy range for absorbing $\g$-rays from distant sources such as blazars and gamma-ray bursts and producing electron positron pairs. In previous work we presented EBL models in the optical through ultraviolet by consistently taking into account the star formation rate (SFR), initial mass function (IMF) and dust extinction, and treating stars on the main sequence as blackbodies. This technique is extended to include post-main sequence stars and self-consistently describe dust absorption and reradiation. We find our best fit model combining the Hopkins and Beacom SFR using the Cole et al. parameterization with the Baldry and Glazebrook IMF agrees with available luminosity density data at a variety of redshifts. Our resulting EBL energy density is quite close to the lower limits from galaxy counts and in some cases below the lower limits, and agrees fairly well with other recent EBL models shortward of about 5 $\mu$m. Deabsorbing TeV $\g$-ray spectra of various blazars with our EBL model gives results consistent with simple shock acceleration theory. We also find that the universe should be optically thin to $\g$-rays with energies less than 20 GeV.

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