Fermi-LAT limits on the γ-ray opacity of the Universe

Rainó, S. and Bouvier, A. and Chen, A. W. and Razzaque, S. and Reimer, A. and Reyes, L. C. (2011) Fermi-LAT limits on the γ-ray opacity of the Universe. Il nuovo cimento C, 34 (3). pp. 253-256. ISSN 1826-9885

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The Fermi Large Area Telescope (LAT) has provided us with a rich sample of extragalactic sources, among which γ-ray blazars with redshift up to z ∼ 3 and Gamma-Ray Bursts with redshift up to z ∼ 4.3, that we have used to probe the interaction via pair production of γ-ray photons above 10GeV with low-energy photons from the Extragalactic Background Light (EBL). The EBL from the infrared to the ultraviolet is difficult to measure directly, but can be constrained with a variety of methods. In this paper we report the method applied to evaluate the EBL attenuation of γ-ray fluxes by comparing the measured energy spectrum of the source and the unabsorbed spectrum above 10 GeV. We place upper limits on the γ-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that EBL intensities at optical-UV wavelengths as large as those predicted by the “baseline” and “fast evolution” models can be ruled out with high confidence. The ensuing upper limits to the EBL opacity are presented.

Item Type: Article
Uncontrolled Keywords: γ-ray ; X- and γ-ray instruments
Subjects: 500 Scienze naturali e Matematica > 530 Fisica
Depositing User: Marina Spanti
Date Deposited: 06 Apr 2020 18:46
Last Modified: 06 Apr 2020 18:46
URI: http://eprints.bice.rm.cnr.it/id/eprint/17279

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