Constraints on the optical-IR extragalactic background from γ-ray absorption studies

AbstractVery high energy (VHE ≳0.1 TeV) gamma-rays from extragalactic sources, interacting by γ-γ collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of direct measurements. The limits depend however on our knowledge of the physics of the gamma-ray sources. After clarifying the interplay between background light and VHE spectra, I summarize the extent and validity of the obtainable limits, and where future improvements can be expected.

Download Full-text

Very high energy gamma-ray absorption via localized diffuse radiation fields

10.1063/1.4772381 ◽

2012 ◽

Cited By ~ 1

Author(s):

Andreas Maurer ◽

Josefa Becerra-Gonzalez ◽

Martin Raue ◽

Dieter Horns

Keyword(s):

Gamma Ray ◽

Diffuse Radiation ◽

High Energy ◽

High Energy Gamma ◽

Radiation Fields ◽

Very High Energy ◽

Energy Gamma ◽

Very High

Download Full-text

Very high energy neutrino expectation from Fanaroff-Riley I sources

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315002136 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 169-174

Author(s):

Antonio Marinelli ◽

Nissim Fraija

Keyword(s):

Gamma Rays ◽

Gamma Ray ◽

Event Rate ◽

High Energy ◽

Spectral Energy ◽

Energy Distributions ◽

Very High Energy ◽

Tev Gamma Rays ◽

Very High ◽

Centaurus A

AbstractFanaroff-Riley I radiogalaxies have been observed in TeV gamma-rays during the last decades. The origin of the emission processes related with this energy band is still under debate. Here we consider the case of the two closest Fanaroff-Riley I objects: Centaurus A and M87. Their entire broadband spectral energy distributions and variability fluxes show evidences that leptonic models are not sufficient to explain their fluxes above 100 GeV. Indeed, both objects have been imaged by LAT instrument aboard of Fermi telescope with measured spectra well connected with one-zone leptonic models. However, to explain the TeV spectra obtained with campaigns by H.E.S.S., for Centaurus A, and by VERITAS, MAGIC and H.E.S.S. for M87, different emission processes must be introduced. In this work we introduce hadronic scenarios to describe the TeV gamma-ray fluxes observed and to obtain the expected neutrino counterparts for each considered TeV campaign. With the obtained neutrino spectra we calculate, through Monte Carlo simulations, the expected neutrino event rate in a hypothetical Km3 neutrino telescope and we compare the results with what has been observed by IceCube experiment up to now.

Download Full-text

Effect of axion-like particles on the spectrum of the extragalactic gamma-ray background

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2021/11/030 ◽

2021 ◽

Vol 2021 (11) ◽

pp. 030

Author(s):

Yun-Feng Liang ◽

Xing-Fu Zhang ◽

Ji-Gui Cheng ◽

Hou-Dun Zeng ◽

Yi-Zhong Fan ◽

...

Keyword(s):

Gamma Ray ◽

Small Region ◽

High Energy ◽

Extragalactic Background Light ◽

Background Light ◽

Very High Energy ◽

The Universe ◽

Very High

Abstract Axion-like particles (ALPs) provide a feasible explanation for the observed lower TeV opacity of the Universe. If the anomaly TeV transparency is caused by ALPs, then the fluxes of distant extragalactic sources will be enhanced at photon energies beyond TeV, resulting in an enhancement of the observed extragalactic gamma-ray background (EGB) spectrum. In this work, we have investigated the ALP modulation on the EGB spectrum at TeV energies. Our results show that in the most optimistic case, the existence of ALPs can cause the EGB spectrum to greatly deviate from the prediction of a pure extragalactic-background-light (EBL) absorption scenario. The deviation occurs at approximately ≳1 TeV, and the current EGB measurements by Fermi-LAT cannot identify such an effect. We also find that most of the sensitive ALP parameters have been ruled out by existing constraints, leaving only a small region of unrestricted parameters that can be probed using the EGB effect investigated in this work. Observations from forthcoming very-high-energy instruments like LHAASO and CTA may be beneficial for the study of this effect.

Download Full-text