1. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China 2. University of Chinese Academy of Sciences, Beijing 100049, China
The Tibet ASγ experiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk, with the highest energy up to 957 TeV. These diffuse gamma rays are most likely the hadronic origin by cosmic ray (CR) interaction with interstellar gas in the galaxy. This measurement provides direct evidence to the hypothesis that the Galactic Cosmic Rays (GCRs) can be accelerated beyond PeV energies. In this work, we try to explain the sub-PeV diffuse gamma-ray spectrum with different CR propagation models. We find that there is a tension between the sub-PeV diffuse gamma-ray and the local CR spectrum. To describe the sub-PeV diffuse gamma-ray flux, it generally requires larger local CR flux than measurement in the knee region. We further calculate the PeV neutrino flux from the CR propagation model. Even all of these sub-PeV diffuse gamma rays originate from the propagation, the Galactic Neutrinos (GNs) only account for less than ~15% of observed flux, most of which are still from extragalactic sources.
M. Nagano , T. Hara , Y. Hatano , N. Hayashida , S. Kawaguchi , K. Kamata , T. Kifune , and Y. Mizumoto , Energy spectrum of primary cosmic rays between 1014.5 and 1018 eV, J. Phys. G 10 (9), 1295 (1984) https://doi.org/10.1088/0305-4616/10/9/016
2
M. A. K. Glasmacher , M. A. Catanese , M. C. Chantell , et al., The cosmic ray energy spectrum between 1014 and 1016 eV, Astropart. Phys. 10 (4), 291 (1999) https://doi.org/10.1016/S0927-6505(98)00070-X
3
M. Aglietta , B. Alessandro , P. Antonioli , F. Arneodo , L. Bergamasco , et al., The cosmic ray primary composition in the “knee” region through the EAS electromagnetic and muon measurements at EAS-TOP, Astropart. Phys. 21 (6), 583 (2004) https://doi.org/10.1016/j.astropartphys.2004.04.005
4
T. Antoni , W. D. Apel , A. F. Badea , K. Bekk , A. Bercuci , et al., KASCADE measurements of energy spectra for elemental groups of cosmic rays: Results and open problems, Astropart. Phys. 24 (2), 1-2 (2005) https://doi.org/10.1016/j.astropartphys.2005.04.001
5
M. Amenomori , X. J. Bi , D. Chen , S. W. Cui , Danzengluobu, et al., The all-particle spectrum of primary cosmic rays in the wide energy range from 1014 to 1017 eV observed with the Tibet-III air-shower array, Astrophys. J. 678 (2), 1165 (2008) https://doi.org/10.1086/529514
R. Aloisio , P. Blasi , I. De Mitri , and S. Petrera , Selected topics in cosmic ray physics, arXiv: 1707.06147 (2017)
8
W. Baade and F. Zwicky , Cosmic rays from super-novae, Contributions from the Mount Wilson Observatory 3, 79 (1934)
9
R. Abbasi , Y. Abdou , T. Abu-Zayyad , M. Ackermann , J. Adams , et al., Observation of anisotropy in the Galactic cosmic-ray arrival directions at 400 TeV with IceCube, Astrophys. J. 746 (1), 33 (2012) https://doi.org/10.1088/0004-637X/746/1/33
10
M. G. Aartsen , K. Abraham , M. Ackermann , J. Adams , J. A. Aguilar , et al., Anisotropy in cosmic-ray arrival directions in the southern hemisphere based on six years of data from the IceCube detector, Astrophys. J. 826 (2), 220 (2016) https://doi.org/10.3847/0004-637X/826/2/220
11
M. Amenomori , X. J. Bi , D. Chen , T. L. Chen , W. Y. Chen , et al., Northern sky Galactic cosmic ray anisotropy between 10 and 1000 TeV with the Tibet air shower array, Astrophys. J. 836 (2), 153 (2017) https://doi.org/10.3847/1538-4357/836/2/153
12
HESS Collaboration, Acceleration of petaelectronvolt protons in the Galactic centre, Nature 531 (7595), 476 (2016) https://doi.org/10.1038/nature17147
13
The Tibet ASγ Collaboration, M. Amenomori, Y. W. Bao, et al., Potential PeVatron supernova remnant G106.3+2.7 seen in the highest-energy gamma rays, Nat. Astron. 5, 460 (2021) https://doi.org/10.1038/s41550-020-01294-9
14
A. U. Abeysekara , A. Albert , R. Alfaro , et al., HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon, arXiv: 2103.06820 (2021)
15
DAMPE Collaboration, Direct detection of a break in the teraelectronvolt cosmic-ray spectrum of electrons and positrons, Nature 552 (7683), 63 (2017) https://doi.org/10.1038/nature24475
16
D. Kerszberg for the HESS Collaboration, The cosmic-ray electron spectrum measured with H.E.S.S. (2017)
17
A. Borione , M. A. Catanese , M. C. Chantell , C. E. Covault , J. W. Cronin , et al., Constraints on gamma-ray emission from the Galactic plane at 300 TeV, Astrophys. J. 493 (1), 175 (1998) https://doi.org/10.1086/305096
18
W. D. Apel , J. C. Arteaga-Velázquez , K. Bekk , M. Bertaina , J. Blümer , et al., KASCADE-Grande limits on the isotropic diffuse gamma-ray flux between 100 TeV and 1 EeV, Astrophys. J. 848 (1), 1 (2017) https://doi.org/10.3847/1538-4357/aa8bb7
19
M. Amenomori , Y. W. Bao , X. J. Bi , D. Chen , T. L. Chen , et al., First detection of sub-PeV diffuse gamma rays from the Galactic disk: Evidence for ubiquitous Galactic cosmic rays beyond PeV energies, Phys. Rev. Lett. 126 (14), 141101 (2021) https://doi.org/10.1103/PhysRevLett.126.141101
20
R. Y. Liu and X. Y. Wang , Origin of Galactic sub PeV diffuse gamma-ray emission: Constraints from high-energy neutrino observations, Astrophys. J. Lett. 914 (1), L7 (2021) https://doi.org/10.3847/2041-8213/ac02c5
21
V. Vecchiotti , F. Zuccarini , F. L. Villante , and G. Pagliaroli , Unresolved sources naturally contribute to PeV γ-ray diffuse emission observed by Tibet ASγ, arXiv: 2107.14584 (2021)
22
S. Koldobskiy , A. Neronov , and D. Semikoz , Pion decay model of the Tibet-ASγ PeV gamma-ray signal, Phys. Rev. D 104 (4), 043010 (2021) https://doi.org/10.1103/PhysRevD.104.043010
23
P. P. Zhang , B. Q. Qiao , Q. Yuan , S. W. Cui , and Y. Q. Guo , Ultrahigh-energy diffuse gamma ray emission from cosmic-ray interactions with the medium surrounding acceleration sources, Phys. Rev. D 105 (2), 023002 (2022) https://doi.org/10.1103/PhysRevD.105.023002
24
IceCube Collaboration, Evidence for high-energy extraterrestrial neutrinos at the IceCube detector, Science 342 (6161), 1242856 (2013) https://doi.org/10.1126/science.1242856
25
M. G. Aartsen , R. Abbasi , Y. Abdou , M. Ackermann , J. Adams , et al., First observation of PeV-energy neutrinos with IceCube, Phys. Rev. Lett. 111 (2), 021103 (2013) https://doi.org/10.1103/PhysRevLett.111.021103
26
M. G. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Observation of high-energy astrophysical neutrinos in three years of IceCube data, Phys. Rev. Lett. 113 (10), 101101 (2014) https://doi.org/10.1103/PhysRevLett.113.101101
27
M. G. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Time integrated neutrino source searches with 10 years of IceCube data, Phys. Rev. Lett. 124 (5), 051103 (2020) https://doi.org/10.1103/PhysRevLett.124.051103
28
M. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A, Science 361 (6398), eaat1378 (2018) https://doi.org/10.1126/science.aat1378
29
M. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert, Science 361 (6398), 147 (2018) https://doi.org/10.1126/science.aat2890
30
M. G. Aartsen , K. Abraham , M. Ackermann , J. Adams , J. A. Aguilar , et al., A combined maximum-likelihood analysis of the high energy astrophysical neutrino flux measured with Ice Cube, Astrophys. J. 809 (1), 98 (2015) https://doi.org/10.1088/0004-637X/809/1/98
31
Y. Q. Guo , H. B. Hu , Q. Yuan , Z. Tian , and X. J. Gao , Pinpointing the knee of cosmic rays with diffuse PeV γ-rays and neutrinos, Astrophys. J. 795 (1), 100 (2014) https://doi.org/10.1088/0004-637X/795/1/100
Q. Yuan , S. J. Lin , K. Fang , and X. J. Bi , Propagation of cosmic rays in the AMS-02 era, Phys. Rev. D 95 (8), 083007 (2017) https://doi.org/10.1103/PhysRevD.95.083007
34
O. Adriani , G. C. Barbarino , G. A. Bazilevskaya , R. Bellotti , M. Boezio , et al., PAMELA measurements of cosmicray proton and helium spectra, Science 332 (6025), 69 (2011) https://doi.org/10.1126/science.1199172
35
P. Blasi and E. Amato , Diffusive propagation of cos mic rays from supernova remnants in the Galaxy (II): Anisotropy, J. Cosmol. Astropart. Phys. 2012 (1), 11 (2012) https://doi.org/10.1088/1475-7516/2012/01/011
36
W. Liu , X. J. Bi , S. J. Lin , B. B. Wang , and P. F. Yin , Excesses of cosmic ray spectra from a single nearby source, Phys. Rev. D 96 (2), 023006 (2017) https://doi.org/10.1103/PhysRevD.96.023006
W. Liu , Y.-Q. Guo , and Q. Yuan , Indication of nearby source signatures of cosmic rays from energy spectra and anisotropies, J. Cosmol. Astropart. Phys. 2019 (10), 010 (2019) https://doi.org/10.1088/1475-7516/2019/10/010
39
B.-Q. Qiao , W. Liu , Y.-Q. Guo , and Q. Yuan , Anisotropies of different mass compositions of cosmic rays, J. Cosmol. Astropart. Phys. 2019 (12), 007 (2019) https://doi.org/10.1088/1475-7516/2019/12/007
40
Y. Q. Guo and Q. Yuan , Understanding the spectral hard-enings and radial distribution of Galactic cosmic rays and Fermi diffuse γ rays with spatially-dependent propagation, Phys. Rev. D 97 (6), 063008 (2018) https://doi.org/10.1103/PhysRevD.97.063008
41
Y. Q. Guo , Z. Tian , and C. Jin , Spatial-dependent propagation of cosmic rays results in the spectrum of proton, ratios of P/P, and B/C, and anisotropy of nuclei, Astrophys. J. 819, 54 (2016) https://doi.org/10.3847/0004-637X/819/1/54
42
W. Liu , Y. H. Yao , and Y. Q. Guo , Revisiting the spatially dependent propagation model with the latest observations of cosmic-ray nuclei, Astrophys. J. 869 (2), 176 (2018) https://doi.org/10.3847/1538-4357/aaef39
43
P. Blasi , E. Amato , and P. D. Serpico , Spectral breaks as a signature of cosmic ray induced turbulence in the galaxy, Phys. Rev. Lett. 109 (6), 061101 (2012) https://doi.org/10.1103/PhysRevLett.109.061101
44
E. S. Seo and V. S. Ptuskin , Stochastic reacceleration of cosmic rays in the interstellar medium, Astrophys. J. 431, 705 (1994) https://doi.org/10.1086/174520
45
G. Case and D. Bhattacharya , Revisiting the Galactic supernova remnant distribution, Astron. Astrophys. Suppl. 120, 437 (1996)
M. Aguilar , L. A. Cavasonza , G. Ambrosi , et al., Precision measurement of the boron to carbon flux ratio in cosmic rays from 1.9 GV to 2.6 TV with the alpha magnetic spectrometer on the International Space Station, Phys. Rev. Lett. 117 (23), 231102 (2016) https://doi.org/10.1103/PhysRevLett.117.231102
48
Y. S. Yoon , T. Anderson , A. Barrau , N. B. Conklin , S. Coutu , et al., Proton and helium spectra from the CREAM-III flight, Astrophys. J. 839 (1), 5 (2017) https://doi.org/10.3847/1538-4357/aa68e4
49
Q. An , R. Asfandiyarov , P. Azzarello , P. Bernardini , X. J. Bi , et al., Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite, Sci. Adv. 5 (9), eaax3793 (2019) https://doi.org/10.1126/sciadv.aax3793
50
M. Aguilar , D. Aisa , B. Alpat , A. Alvino , G. Ambrosi , et al., Precision measurement of the proton flux in primary cosmic rays from rigidity 1 GV to 1.8 TV with the alpha magnetic spectrometer on the International Space Station, Phys. Rev. Lett. 114 (17), 171103 (2015) https://doi.org/10.1103/PhysRevLett.114.171103
51
M. Aguilar , L. A. Cavasonza , B. Alpat , et al., Observation of the identical rigidity dependence of He, C, and O cosmic rays at high rigidities by the alpha magnetic spectrometer on the International Space Station, Phys. Rev. Lett. 119 (25), 251101 (2017) https://doi.org/10.1103/PhysRevLett.119.251101
52
E. Atkin , V. Bulatov , V. Dorokhov , N. Gorbunov , S. Filippov , et al., First results of the cosmic ray NUCLEON experiment, J. Cosmol. Astropart. Phys. 07, 020 (2017) https://doi.org/10.1088/1475-7516/2017/07/020
53
W. D. Apel , J. C. Arteaga-Velázquez , K. Bekk , M. Bertaina , J. Blümer , et al., KASCADE-Grande measurements of energy spectra for elemental groups of cosmic rays, Astropart. Phys. 47, 54 (2013) https://doi.org/10.1016/j.astropartphys.2013.06.004
54
M. G. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Cosmic ray spectrum and composition from PeV to EeV using 3 years of data from IceTop and IceCube, Phys. Rev. D 100 (8), 082002 (2019) https://doi.org/10.1103/PhysRevD.100.082002
55
J. C. Arteaga-Velázquez , HAWC measurements of the energy spectra of cosmic ray protons, helium and heavy nuclei in the TeV range, arXiv: 2108.03208 (2021)
M. G. Aartsen , R. Abbasi , M. Ackermann , J. Adams , J. A. Aguilar , et al., Cosmic ray spectrum from 250 TeV to 10 PeV using IceTop, Phys. Rev. D 102 (12), 122001 (2020) https://doi.org/10.1103/PhysRevD.102.122001
58
R. Alfaro , C. Alvarez , J. D. Álvarez , R. Arceo , J. C. Arteaga-Velázquez , et al., All particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV, Phys. Rev. D 96 (12), 122001 (2017) https://doi.org/10.1103/PhysRevD.96.122001
59
G. Di Sciascio , Measurement of the Cosmic Ray Energy Spectrum with ARGO-YBJ, arXiv: 1408.6739 (2014)
60
A. D. Panov , J. H. Jr Adams , H. S. Ahn , G. L. Bashinzhagyan , et al., Energy spectra of abundant nuclei of primary cosmic rays from the data of ATIC-2 experiment: Final results, Bull. Russ. Acad. Sci, Physics 73 (5), 564 (2009) https://doi.org/10.3103/S1062873809050098
61
E. V. Atkin , V. L. Bulatov , O. A. Vasiliev , A. G. Voronin , N. V. Gorbunov , et al., Energy Spectra of Cosmic-Ray Protons and Nuclei Measured in the NUCLEON Experiment Using a New Method, Astron. Rep. 63 (1), 66 (2019) https://doi.org/10.1134/S1063772919010013
62
J.-L. Zhang , X.-J. Bi , and H.-B. Hu , Very high energy γ ray absorption by the Galactic interstellar radiation field, Astron. & Astrophys. 449, 641 (2006) https://doi.org/10.1051/0004-6361:20054422
63
I. V. Moskalenko , T. A. Porter , and A. W. Strong , Attenuation of very high energy gamma rays by the milky way interstellar radiation field, Astrophys. J. 640 (2), L155 (2006) https://doi.org/10.1086/503524
64
B. Bartoli , P. Bernardini , X. J. Bi , P. Branchini , A. Budano , et al., Study of the diffuse gamma-ray emission from the Galactic plane with ARGO-YBJ, Astrophys. J. 806 (1), 20 (2015) https://doi.org/10.1088/0004-637X/806/1/20
65
M. D. Kistler and J. F. Beacom , Guaranteed and prospective Galactic TeV neutrino sources, Phys. Rev. D 74 (6), 063007 (2006) https://doi.org/10.1103/PhysRevD.74.063007
66
R. Abbasi , M. Ackermann , J. Adams , et al., The IceCube high-energy starting event sample: Description and flux characterization with 7.5 years of data, arXiv: 2011.03545 (2020)
67
S. Adrián-Martínez , A. Albert , M. André , M. Anghinolfi , G. Anton , et al., Constraints on the neutrino emission from the Galactic Ridge with the ANTARES telescope, Phys. Lett. B 760, 143 (2016) https://doi.org/10.1016/j.physletb.2016.06.051
68
M. G. Aartsen , M. Ackermann , J. Adams , J. A. Aguilar , M. Ahlers , et al., Constraints on Galactic neutrino emission with seven years of IceCube data, Astrophys. J. 849 (1), 67 (2017) https://doi.org/10.3847/1538-4357/aa8dfb
69
F. Aharonian , R. Yang , and E. de Oña Wilhelmi , Massive stars as major factories of Galactic cosmic rays, Nat. Astron. 3 (6), 561 (2019) https://doi.org/10.1038/s41550-019-0724-0
A. M. Bykov , D. C. Ellison , P. E. Gladilin , and S. M. Osipov , Ultrahard spectra of PeV neutrinos from supernovae in compact star clusters, Mon. Not. R. Astron. Soc. 453 (1), 113 (2015) https://doi.org/10.1093/mnras/stv1606
72
A. M. Bykov , A. E. Petrov , M. E. Kalyashova , and S. V. Troitsky , PeV photon and neutrino flares from Galactic gamma-ray binaries, Astrophys. J. Lett. 921 (1), L10 (2021) https://doi.org/10.3847/2041-8213/ac2f3d
73
R. Yang , F. Aharonian , and C. Evoli , Radial distribution of the diffuse γ-ray emissivity in the Galactic disk, Phys. Rev. D 93 (12), 123007 (2016) https://doi.org/10.1103/PhysRevD.93.123007
74
A. W. Strong and I. V. Moskalenko , Propagation of cosmic-ray nucleons in the galaxy, Astrophys. J. 509 (1), 212 (1998) https://doi.org/10.1086/306470
75
A. W. Strong , I. V. Moskalenko , and O. Reimer , Diffuse continuum gamma rays from the galaxy, Astrophys. J. 537 (2), 763 (2000) https://doi.org/10.1086/309038
76
C. Evoli , D. Gaggero , D. Grasso , and L. Maccione . Cosmic ray nuclei, antiprotons and gamma rays in the galaxy: A new diffusion model, J. Cosmol. Astropart. Phys. 10, 018 (2008) https://doi.org/10.1088/1475-7516/2008/10/018
77
C. Evoli , D. Gaggero , A. Vittino , G. Di Bernardo , M. Di Mauro , et al., Cosmic-ray propagation with DRAGON2 (I): Numerical solver and astrophysical ingredients, J. Cosmol. Astropart. Phys. 02, 015 (2017) https://doi.org/10.1088/1475-7516/2017/02/015
