Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei

Breuhaus, M.; Hinton, J. A.; Joshi, Vikas; Reville, Brian; Schoorlemmer, H.

doi:10.1051/0004-6361/202141318

Cited by 14 publications

(11 citation statements)

References 73 publications

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“…We finally note that in order to safely disentangle different interpretations, having more data will be crucial. In particular, we emphasize the role of neutrino measurements in this context (see also Ahlers et al 2016;Gaggero et al 2015a;Fang & Murase 2021;Breuhaus et al 2022). The truly diffuse component is likely to be entirely hadronic above a few TeV, while the sources that could potentially contribute to the unresolved flux are mostly leptonic (namely, pulsar wind nebulae).…”

Section: Discussionmentioning

confidence: 95%

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Galactic diffuse gamma rays meet the PeV frontier

Luque

Gaggero

Grasso

et al. 2023

A&A

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Context. The Tibet ASγ and LHAASO collaborations recently reported the observation of a γ-ray diffuse emission with energy up to the PeV level from the Galactic plane. Aims. We discuss the relevance of non-uniform cosmic-ray transport scenarios and the implications of these results for cosmic-ray physics. Methods. We used the DRAGON and HERMES codes to build high-resolution maps and spectral distributions of that emission for several representative models under the condition that they reproduce a wide set of local cosmic-ray data up to 100 PeV. Results. We show that the energy spectra measured by Tibet ASγ, LHAASO, ARGO-YBJ, and Fermi-LAT in several regions of interest in the sky can all be reasonably described in terms of the emission arising by the Galactic cosmic-ray “sea”. We also show that all our models are compatible with IceTop γ-ray upper limits. Conclusions. We compare the predictions of conventional and space-dependent transport models with those data sets. Although the Fermi-LAT, ARGO-YBJ, and LHAASO preliminary data slightly favor this scenario, due to the still large experimental errors, the poorly known source spectral shape at the highest energies, the potential role of spatial fluctuations in the leptonic component, and a possible larger-than-expected contamination due to unresolved sources, a solid confirmation requires further investigations. We discuss which measurements will be most relevant in order to resolve the remaining degeneracy.

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Section: Discussionmentioning

confidence: 95%

“…As an additional comment, we do not account for CR species heavier than helium since, under reasonable conditions, their contribution to the gamma-ray source term is subdominant (less than 10%) with respect to the expected flux due to proton plus helium production rate (see, e.g., Breuhaus et al 2022 for a recent analysis).…”

Section: Injection Parametersmentioning

confidence: 99%

Galactic diffuse gamma rays meet the PeV frontier

Luque

Gaggero

Grasso

et al. 2023

A&A

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“…The overall effect of the absorption thus depends on the assumed Galactic distributions of cosmic rays and gas, the ISRF model, and the direction in the sky. The dependence on both the choice of ISRF model and details of the cosmic-ray and gas distributions is however only weak (Vernetto & Lipari 2016;Breuhaus et al 2022), in part because the dominant contribution to the absorption stems from interactions with the homogeneous CMB.…”

Section: Gamma-ray Absorptionmentioning

confidence: 99%

“…We calculate this following the prescriptions described in Appendix E of Breuhaus et al (2022). We also assume the same ISRF model (Popescu et al 2017) and analytical descriptions of the distributions of Galactic gas (Ferrière 1998;Ferrière et al 2007) and cosmic rays (Lipari & Vernetto 2018) as used there.…”

Section: Gamma-ray Absorptionmentioning

confidence: 99%

Diffuse Emission of Galactic High-energy Neutrinos from a Global Fit of Cosmic Rays

Schwefer

Mertsch

Wiebusch

2023

ApJ

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In the standard picture of Galactic cosmic rays, a diffuse flux of high-energy gamma rays and neutrinos is produced from inelastic collisions of cosmic-ray nuclei with the interstellar gas. The neutrino flux is a guaranteed signal for high-energy neutrino observatories such as IceCube but has not been found yet. Experimental searches for this flux constitute an important test of the standard picture of Galactic cosmic rays. Both observation and nonobservation would allow important implications for the physics of cosmic-ray acceleration and transport. We present CRINGE, a new model of Galactic diffuse high-energy gamma rays and neutrinos, fitted to recent cosmic-ray data from AMS-02, DAMPE, IceTop, as well as KASCADE. We quantify the uncertainties for the predicted emission from the cosmic-ray model but also from the choice of source distribution, gas maps, and cross sections. We consider the possibility of a contribution from unresolved sources. Our model predictions exhibit significant deviations from older models. Our fiducial model is available at https://doi.org/10.5281/zenodo.7859442 .

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“…It was also discussed how relevant are ultra-high energy gamma-ray measurements (e.g. from Tibet ASγ [28] and future expected ones by LHAASO) as the CR proton spectrum is still not perfectly known in the region of the knee [29,30]. This is due to some discrepancy between KASCADE and IceTop proton knees at about 4 PeV, and to some extent to the discrepancies in the helium knee at about Z × 4 PeV, where Z is the number of protons in the ionized nucleus.…”

Section: The Galactic Plane Fluxesmentioning

confidence: 99%

Selected results from IceCube

Montaruli

2023

J. Phys.: Conf. Ser.

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Neutrino astronomy saw its birth with the discovery by IceCube of a difFuse flux at energies above 60 TeV with intensity comparable to a predicted upper limit to the flux from extra-galactic sources of ultra-high energy cosmic rays (UHECRs). While such an upper limit corresponds to the case of calorimetric sources, in which cosmic rays lose all their energy into photo-pion production, the first statistically significant coincident observation between neutrinos and gamma-rays was observed from a blazar of intriguing nature. A very-high-energy muon event, of most probable neutrino energy of 290 TeV for an E −2.13 spectrum, alerted other observatories triggering a large amount of investigations in many bands of the electromagnetic (EM) spectrum. A high gamma-ray state from the blazar was revealed soon after the event and in a follow up to about 40 days. A posteriori observations also in the optical and in the radio indicated a rise of the flux from the TXS 0506+056 blazar. A previous excess of events of duration of more than 100 d was observed by IceCube with higher significance than the alert itself. These observations triggered more complex modelling than simple one zone proton synchrotron models for proton acceleration in jets of active galactic nuclei (AGNs) and more observations across the EM spectrum. A second evidence was a steady excess of about 50 neutrino events with reconstructed soft spectrum in a sample of lower energy well reconstructed muon events than the alert event. A hot spot was identified in a catalogue of 110 gamma-ray intense emitters and starburst galaxies in a direction compatible to NGC 1068 with significance of 2.9σ. NGC 1068 hosts a mildly relativistic jet in a starburst galaxy, seen not from the jet direction but rather through the torus. This Seyfert II galaxy is at only 14.4 Mpc from the Earth. The source turned out to be also the hottest spot of an all-sky search. Analysed cumulatively, the catalogue excess was 3.3σ with the contribution of NGC 1068 and TXS 0506+056, as expected, and other 2 sources, PKS 1424+240, and GB6 J1542+6129, with similar features to TXS 0506+056, indicating that they might all be Flat Spectrum Radio Quasars (FSRQs). While all these observations and the directions of the measured events contributing to diffuse fluxes hint to their extra-galactic origin, a few percent level contribution might be the end of a lower energy ‘granted’ flux of neutrinos from interactions of cosmic rays in the Galactic Plane. This relevant observation is at the reach of IceCube and other neutrino telescopes. These aspects were discussed at the conference and are summarised in this write up.

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Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei

Cited by 14 publications

References 73 publications

Galactic diffuse gamma rays meet the PeV frontier

Galactic diffuse gamma rays meet the PeV frontier

Diffuse Emission of Galactic High-energy Neutrinos from a Global Fit of Cosmic Rays

Selected results from IceCube

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