ESTIMATION OF THE EXTRAGALACTIC BACKGROUND LIGHT USING TeV OBSERVATIONS OF BL Lac OBJECTS

Sinha, Atreyee; Sahayanathan, S.; Misra, Ranjeev; Godambe, S.; Acharya, B. S.

doi:10.1088/0004-637x/795/1/91

Cited by 20 publications

(16 citation statements)

References 87 publications

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“…The most common procedure used is to vary the level of the EBL until the corrected γ-ray spectrum shows an apparent unphysical behavior [54,56,57,58,59]. More elaborate approaches include the use of multiple source spectra [60,61,62] or multi-wavelength observations and models of the γ-ray spectra to reduce the uncertainties related to the unknown intrinsic spectrum [63,64,65]. Additionally, the shape of the EBL spectrum has been left to vary freely in order to eliminate a model uncertainty [66,67], and the energy range has been extended by including Fermi-LAT observations [68,69,70].…”

Section: Inferring the Optical/near-infrared Background Light From γ-mentioning

confidence: 99%

Gamma rays as probes of the Universe

Horns

Jachołkowska²

2016

Comptes Rendus. Physique

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The propagation of γ rays over very large distances provides new insights on the intergalactic medium and on fundamental physics. On their path to the Earth, γ rays can annihilate with diffuse infrared or optical photons of the intergalactic medium, producing e + e − pairs. The density of these photons is poorly determined by direct measurements due to significant galactic foregrounds. Studying the absorption of γ rays from extragalactic sources at different distances allows the density of low-energy diffuse photons to be measured. Gamma-ray propagation may also be affected by new phenomena predicted by extensions of the Standard Model of particle physics. Lorentz Invariance is violated in some models of Quantum Gravity, leading to an energy-dependent speed of light in vacuum. From differential time-of-flight measurements of the most distant γ-ray bursts and of flaring active galactic nuclei, lower bounds have been set on the energy scale of Quantum Gravity. Another effect that may alter γ-ray propagation is predicted by some models of String Theory, namely the mixing of the γ ray with a light fundamental boson called an "axion-like particle", which does not interact with low-energy photons. Such a mixing would make the Universe more transparent to γ rays than what would otherwise be, in a sense it decreases the amount of modification to the spectrum that comes from the extragalactic background light. The present status of the search for all these phenomena in γ-ray astronomy is reviewed.To cite this article: Horns, D. and Jacholkowska, A., C.R. Physique XX (2016). Résumé La propagation des photons γ sur de très grandes distances nous permet de sonder le milieu intergalactique et fournit des tests de physique fondamentale. Au cours de leur chemin vers la Terre, ceux-ci peuvent s'annihiler avec les photons infrarouges et optiques du milieu intergalactique, produisant ainsi des paires e + e − . L'absorption des photons γémis par des sources extragalactiquesà différentes distances permet de mesurer ce fond diffus, par ailleurs très mal connu par des mesures directes en raison des importants rayonnements d'avant-plan dusà la Galaxie. La propagation des photons γ peut aussiêtre affectée par de nouveaux phénomènes prédits par des extensions du modèle standard de la physique des particules. L'invariance de Lorentz est violée dans certains modèles de gravité quantique où la vitesse de la lumière dans le vide varie avec l'énergie du photon γ. Les mesures différentielles de temps de vol sur les sursauts γ et sur leséruptions de noyaux actifs de galaxie ont permis d'obtenir des bornes inférieures sur l'échelle d'énergie de la gravité quantique. Un autre effet pouvant affecter la propagation des photons γ est prédit par des modèles de la théorie des cordes. Il s'agit du mélange quantique entre le photon et une particule légère de type "axion" qui n'interagit pas avec les photons infrarouges et optiques. En diminuant dans les spectres l'empreinte de l'absorption par le fond diffus, ce mélange rendrait l'Univers plus ...

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Section: Inferring the Optical/near-infrared Background Light From γ-mentioning

confidence: 99%

Gamma rays as probes of the Universe

Horns

Jachołkowska²

2016

Comptes Rendus. Physique

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“…Furthermore, published spectral points are not usually released together with their covariance matrix. Using this additional information, these results are expected to be more robust than similar studies only using published spectra from different Cherenkov telescopes (e.g., Orr et al 2011;Meyer et al 2012;Sinha et al 2014;Biteau & Williams 2015). This paper is organized as follows.…”

Section: Introductionmentioning

confidence: 96%

Measurement of the EBL spectral energy distribution using the VHE γ-ray spectra of H.E.S.S. blazars

Abdalla¹,

Abramowski²,

Aharonian³

et al. 2017

A&A

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Very high-energy γ rays (VHE, E 100 GeV) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. The transparency of the Universe to VHE γ rays is then directly related to the spectral energy distribution (SED) of the EBL. The observation of features in the VHE energy spectra of extragalactic sources allows the EBL to be measured, which otherwise is very difficult. An EBL model-independent measurement of the EBL SED with the H.E.S.S. array of Cherenkov telescopes is presented. It was obtained by extracting the EBL absorption signal from the reanalysis of high-quality spectra of blazars. From H.E.S.S. data alone the EBL signature is detected at a significance of 9.5σ, and the intensity of the EBL obtained in different spectral bands is presented together with the associated γ-ray horizon.

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“…At lower energies, in the TeV range, photons interact by the Breit-Wheeler process with the EBL [6][7][8]. Hence the observation of TeV radiation from distant (d > 100 Mpc) extragalactic objects provides important constraints on the EBL [9][10][11].…”

Section: Processes Involving Photonsmentioning

confidence: 99%

Cosmic absorption of ultra high energy particles

Ruffini

Vereshchagin

Xue

2016

Astrophys Space Sci

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Abstract. This paper summarizes the limits on propagation of ultra high energy particles in the Universe, set up by their interactions with cosmic background of photons and neutrinos. By taking into account cosmic evolution of these backgrounds and considering appropriate interactions we derive the mean free path for ultra high energy photons, protons and neutrinos. For photons the relevant processes are the Breit-Wheeler process as well as the double pair production process. For protons the relevant reactions are the photopion production and the Bethe-Heitler process. We discuss the interplay between the energy loss length and mean free path for the Bethe-Heitler process. Neutrino opacity is determined by its scattering off the cosmic background neutrino. We compute for the first time the high energy neutrino horizon as a function of its energy.

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ESTIMATION OF THE EXTRAGALACTIC BACKGROUND LIGHT USING TeV OBSERVATIONS OF BL Lac OBJECTS

Cited by 20 publications

References 87 publications

Gamma rays as probes of the Universe

Gamma rays as probes of the Universe

Measurement of the EBL spectral energy distribution using the VHE γ-ray spectra of H.E.S.S. blazars

Cosmic absorption of ultra high energy particles

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