Extragalactic Gamma-ray Background Radiation from Beamed and Unbeamed Active Galactic Nuclei

Inoue, Yoshiyuki

doi:10.1088/1742-6596/355/1/012037

Cited by 6 publications

(7 citation statements)

References 24 publications

(45 reference statements)

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“…The key parameters in GLF have carefully been determined to match the observed flux and redshift distribution of EGRET blazars by a likelihood analysis. The predicted extragalactic gamma-ray background (EGB) spectrum [29] including contributions from Seyferts [44] and radio galaxies [45] are in good agreement with the EGB spectrum reported by Fermi [46,47]. Predicted blazar GLF [29] reproduces the local GLF of flat-spectrum radio quasars (FSRQs) well [35], although it slightly underestimates the number of FSRQs at z 1.…”

Section: Blazar Gamma-ray Luminosity Function and Primary Spectrumsupporting

confidence: 83%

Prospects for future very high-energy gamma-ray sky survey: Impact of secondary gamma rays

Inoue

Kalashev

Kusenko

2014

Astroparticle Physics

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Very high-energy gamma-ray measurements of distant blazars can be well explained by secondary gamma rays emitted by cascades induced by ultra-high-energy cosmic rays. The secondary gamma rays will enable one to detect a large number of blazars with future ground based gamma-ray telescopes such as Cherenkov Telescope Array (CTA). We show that the secondary emission process will allow CTA to detect 100, 130, 150, 87, and 8 blazars above 30 GeV, 100 GeV, 300 GeV, 1 TeV, and 10 TeV, respectively, up to z ∼ 8 assuming the intergalactic magnetic field (IGMF) strength B = 10 −17 G and an unbiased all sky survey with 0.5 hr exposure at each Field of View, where total observing time is ∼ 540 hr. These numbers will be 79, 96, 110, 63, and 6 up to z ∼ 5 in the case of B = 10 −15 G. This large statistics of sources will be a clear evidence of the secondary gamma-ray scenarios and a new key to studying the IGMF statistically. We also find that a wider and shallower survey is favored to detect more and higher redshift sources even if we take into account secondary gamma rays.

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Section: Blazar Gamma-ray Luminosity Function and Primary Spectrumsupporting

confidence: 83%

Prospects for future very high-energy gamma-ray sky survey: Impact of secondary gamma rays

Inoue

Kalashev

Kusenko

2014

Astroparticle Physics

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“…In our canonical model, we assume the distribution reported in Γ SF-AGN(non-SB) = Γ NG and Γ SF-AGN(SB) = Γ SB . 3 Note that, in the picture of cosmic-ray diffusion, the spectral index difference δ CR ≡ Γ NG − Γ SB ∼ 0.5 is interpreted as the energy dependence of the diffusion coefficient.…”

Section: Gamma-ray Fluxmentioning

confidence: 99%

Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

Tamborra

Ando

Murase

2014

J. Cosmol. Astropart. Phys.

262

321

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Abstract. Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce highenergy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1-2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E −2.15 are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.

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“…(2.1) in the transparent limit. Note that cascade contributions from this power-law component are insignificant when α is sufficiently larger than 2 [e.g., 48,49]. One should keep in mind that the real situation can be complicated by various astrophysical contributions especially from blazars and star-forming/star-burst galaxies [see a review 33, and references therein].…”

Section: Cascades Induced By Primary Vhe/uhe Gamma Raysmentioning

confidence: 99%

Gamma-ray and neutrino backgrounds as probes of the high-energy universe: hints of cascades, general constraints, and implications for TeV searches

Murase

Beacom

Takami³

2012

J. Cosmol. Astropart. Phys.

113

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Recent observations of isotropic diffuse backgrounds by Fermi and IceCube allow us to get more insight into distant very-high-energy (VHE) and ultra-high-energy (UHE) gamma-ray/neutrino emitters, including cosmic-ray accelerators/sources. First, we investigate the contribution of intergalactic cascades induced by gamma-rays and/or cosmic rays (CRs) to the diffuse gamma-ray background (DGB) in view of the latest Fermi data. We identify a possible "VHE Excess" from the fact that the Fermi data are well above expectations for an attenuated power law, and show that cascades induced by VHE gamma rays (above ∼ 10 TeV) and/or VHECRs (below ∼ 10 19 eV) may significantly contribute to the DGB above ∼ 100 GeV. The relevance of the cascades is also motivated by the intergalactic cascade interpretations of extreme TeV blazars such as 1ES 0229+200, which suggest very hard intrinsic spectra. This strengthens the importance of future detailed VHE DGB measurements. Then, more conservatively, we derive general constraints on the cosmic energy budget of high-energy gamma rays and neutrinos based on recent Fermi and IceCube observations of extragalactic background radiation. We demonstrate that these multi-messenger constraints are useful and the neutrino limit is very powerful for VHE/UHE hadronic sources. Furthermore, we show the importance of constraints from individual source surveys by future imaging atmospheric Cherenkov telescopes such as Cherenkov Telescope Array, and demonstrate that the cascade hypothesis for the VHE DGB can be tested by searching for distant emitters of cascaded gamma rays.

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Extragalactic Gamma-ray Background Radiation from Beamed and Unbeamed Active Galactic Nuclei

Cited by 6 publications

References 24 publications

Prospects for future very high-energy gamma-ray sky survey: Impact of secondary gamma rays

Prospects for future very high-energy gamma-ray sky survey: Impact of secondary gamma rays

Star-forming galaxies as the origin of diffuse high-energy backgrounds: gamma-ray and neutrino connections, and implications for starburst history

Gamma-ray and neutrino backgrounds as probes of the high-energy universe: hints of cascades, general constraints, and implications for TeV searches

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