Ground-based gamma-ray astronomy

Lemoine‐Goumard, M.

doi:10.22323/1.236.0012

Cited by 5 publications

(9 citation statements)

References 49 publications

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“…Hence, at the heights above 10 km where the initial development of the shower takes place, charged pions will reinteract for energies in excess of ∼ 30 GeV (for showers with large zenith angles, which develop higher in the atmosphere, pions may be able to decay at even higher energies). The number of generations of hadronic interactions taking place before the charged pions can finally decay is n d ≃ log(E 0 /E d )/ log(n tot ), so that if one adopts as a typical average multiplicity n tot ≃ 20, one gets that n d ≃ 5-6 for EeV primaries 3 . A pictorial view of the main characteristics of hadronic showers is given in the right side of Fig.…”

Section: The Physics Of Air Showersmentioning

confidence: 99%

“…Actually, imaging the Cherenkov emission with telescopes, in observatories such as H.E.S.S. or in the future with CTA (see [3] for a recent overview and references), it is also possible to do astronomy in the energy range between tens of GeV and up to tens of TeV by discriminating the showers initiated by photons from the much larger background from hadronic showers. Using arrays of non-imaging detectors of atmospheric Cherenkov light, such as those in TUNKA or Yakutsk, it is possible to study CRs from PeV up to EeV energies, while the detection of fluorescence light becomes competitive above 100 PeV.…”

Section: Introductionmentioning

confidence: 99%

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Progress in high-energy cosmic ray physics

Mollerach

Roulet

2018

Progress in Particle and Nuclear Physics

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We review some of the recent progress in our knowledge about high-energy cosmic rays, with an emphasis on the interpretation of the different observational results. We discuss the effects that are relevant to shape the cosmic ray spectrum and the explanations proposed to account for its features and for the observed changes in composition. The physics of air-showers is summarized and we also present the results obtained on the proton-air cross section and on the muon content of the showers. We discuss the cosmic ray propagation through magnetic fields, the effects of diffusion and of magnetic lensing, the cosmic ray interactions with background radiation fields and the production of secondary neutrinos and photons. We also consider the cosmic ray anisotropies, both at large and small angular scales, presenting the results obtained from the TeV up to the highest energies and discuss the models proposed to explain their origin.Comment: 48 pages, to appear in Progress in Particle and Nuclear Physics (2017

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Section: The Physics Of Air Showersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Progress in high-energy cosmic ray physics

Mollerach

Roulet

2018

Progress in Particle and Nuclear Physics

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“…We compare our results to γ-ray observations of the Fermi bubbles by the Fermi-LAT at GeV energies (black squares), the 95% confidence upper limits on the TeV γ-ray flux recorded by HAWC (black solid bars), the 90% confidence upper limits on ultrahigh-energy gamma rays by CASA-MIA scaled to the bubbles region (olive upper limits; [23,32]), and the 90% confidence upper limit on the neutrino flux at TeV-PeV energies as calculated in this work (red upper limit). We additionally show the projected sensitivity from 100 hr of CTA observations (grey dotted; [33]), 5 yr of HiSCOR observations (green dotted; [34]), and 1 yr of LHASSO observations (pink dotted; [35]) converted to the region of the Fermi bubbles following [23], assuming that these detectors would be able to view (or have viewed) the Fermi bubbles continuously for assumed periods. In the hadronic scenario (thick lines), the maximum neutrino flux allowed by the Fermi-LAT and HAWC measurements does not produce a significant IceCube flux at high neutrino energies.…”

Section: Hawc Observations Of the Fermi Bubblesmentioning

confidence: 99%

IceCube and HAWC constraints on very-high-energy emission from the Fermi bubbles

Fang

Linden

et al. 2017

Phys. Rev. D

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The nature of the γ-ray emission from the Fermi bubbles is unknown. Both hadronic and leptonic models have been formulated to explain the peculiar γ-ray signal observed by the Fermi-LAT between 0.1-500 GeV. If this emission continues above ∼30 TeV, hadronic models of the Fermi bubbles would provide a significant contribution to the high-energy neutrino flux detected by the IceCube observatory. Even in models where leptonic γ-rays produce the Fermi bubbles flux at GeV energies, a hadronic component may be observable at very high energies. The combination of IceCube and HAWC measurements have the ability to distinguish these scenarios through a comparison of the neutrino and γ-ray fluxes at a similar energy scale. We examine the most recent four-year dataset produced by the IceCube collaboration and find no evidence for neutrino emission originating from the Fermi bubbles. In particular, we find that previously suggested excesses are consistent with the diffuse astrophysical background with a p-value of 0.22 (0.05 in an extreme scenario that all the IceCube events that overlap with the bubbles come from them). Moreover, we show that existing and upcoming HAWC observations provide independent constraints on any neutrino emission from the Fermi bubbles, due to the close correlation between the γ-ray and neutrino fluxes in hadronic interactions. The combination of these results disfavors a significant contribution from the Fermi bubbles to the IceCube neutrino flux.

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“…Some other classes of extragalactic objects have been confirmed as VHE gamma-rays emitters like radio galaxies, Flat Spectrum Radio Quasars and star-bust galaxies. For recent review of the status of the gamma-ray astronomy see, e.g., [15].…”

Section: Gamma-ray Astronomymentioning

confidence: 99%

The Cherenkov Telescope Array

Bigongiari

2016

Nuclear and Particle Physics Proceedings

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The Cherenkov Telescope Array (CTA) is planned to be the next generation ground based observatory for very high energy (VHE) gamma-ray astronomy. Gamma-rays provide a powerful insight into the non-thermal universe and hopefully a unique probe for new physics. Imaging Cherenkov telescopes have already discovered more than 170 VHE gamma-ray emitters providing plentiful of valuable data and clearly demonstrating the power of this technique. In spite of the impressive results there are indications that the known sources represent only the tip of the iceberg. A major step in sensitivity is needed to increase the number of detected sources, observe short time-scale variability and improve morphological studies of extended sources. An extended energy coverage is advisable to observe far-away extragalactic objects and improve spectral analysis. CTA aims to increase the sensitivity by an order of magnitude compared to current facilities, to extend the accessible gamma-ray energies from a few tens of GeV to a hundred of TeV, and to improve on other parameters like angular and energy resolution. CTA will provide moreover a full sky-coverage by featuring an array of imaging atmospheric Cherenkov telescopes in both hemispheres.This paper presents an overview of the technical design and summarize the current status of the project. CTA prospects for some key science topics like the origin of relativistic cosmic particles, the acceleration mechanisms in extreme environments such as neutron stars and black holes and searches for Dark Matter are discussed.

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Ground-based gamma-ray astronomy

Cited by 5 publications

References 49 publications

Progress in high-energy cosmic ray physics

Progress in high-energy cosmic ray physics

IceCube and HAWC constraints on very-high-energy emission from the Fermi bubbles

The Cherenkov Telescope Array

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