pith. sign in

arxiv: 2606.30764 · v1 · pith:LV2Q4FKZnew · submitted 2026-06-29 · 🌌 astro-ph.HE · astro-ph.GA

Active Galactic Nuclei as high-energy neutrino sources

Filippo D'Ammando (INAF-IRA Bologna) This is my paper

Pith reviewed 2026-07-01 02:00 UTC · model grok-4.3

classification 🌌 astro-ph.HE astro-ph.GA
keywords active galactic nucleihigh-energy neutrinosIceCubeblazarsneutrino sourcesmulti-messenger astronomyTXS 0506+056NGC 1068
0
0 comments X

The pith

IceCube reports neutrino events possibly linked to both the radio-loud AGN TXS 0506+056 and the radio-quiet AGN NGC 1068, though the gamma-ray blazar population accounts for only a small fraction of the total astrophysical neutrino flux.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This review surveys searches for correlations between IceCube high-energy neutrinos and active galactic nuclei. It emphasizes that the gamma-ray blazar population contributes only a minor share of the observed neutrino flux. Possible individual associations are discussed for TXS 0506+056 and NGC 1068, along with other claimed blazar links that remain controversial. Neutrino production mechanisms proposed for these objects are examined, and the paper outlines open questions for upcoming facilities and multi-messenger observations.

Core claim

The IceCube Collaboration has reported high-energy neutrino events that may come from both the radio-loud AGN TXS 0506+056 and the radio-quiet AGN NGC 1068, while the gamma-ray blazar population accounts for only a small fraction of the total astrophysical neutrino flux. Other possible associations between neutrino events and individual blazars have been claimed with mixed results. The properties of these sources and different neutrino production mechanisms are discussed.

What carries the argument

Spatial and temporal correlations between individual high-energy neutrino events and the sky positions of specific AGN, together with models of neutrino production in AGN jets or coronae.

If this is right

  • Individual AGN such as TXS 0506+056 and NGC 1068 could contribute measurably to the neutrino flux even if the full blazar population does not.
  • Neutrino production may occur through distinct channels in radio-loud jets versus radio-quiet environments.
  • Multi-frequency monitoring combined with neutrino alerts will be required to test these candidate sources.
  • Future neutrino observatories will help determine whether AGN dominate the remaining unexplained portion of the astrophysical flux.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the associations hold, radio-quiet AGN may represent a previously under-appreciated channel for high-energy neutrino production independent of strong jets.
  • Confirmation would strengthen the case that AGN also accelerate a fraction of ultra-high-energy cosmic rays, linking neutrino and cosmic-ray observations.
  • Population-level limits on blazars would then direct attention toward other AGN subclasses or entirely different source classes for the bulk of the flux.

Load-bearing premise

The reported spatial and temporal coincidences between neutrino events and specific AGN reflect genuine physical associations rather than chance alignments or background fluctuations.

What would settle it

A statistical analysis demonstrating that the probability of the observed neutrino-AGN coincidences arising from background alone exceeds the significance level reported by IceCube would refute the proposed associations.

read the original abstract

Identifying the sources of the high-energy astrophysical neutrinos has been one of the main topics in astrophysics since the first observation of high-energy neutrinos by the IceCube Neutrino Observatory. Active Galactic Nuclei (AGN) are sources of high-energy gamma-rays and are considered to be promising candidates to be sources of high-energy neutrinos and ultra-high energy cosmic rays as well. However, several studies suggest that the neutrino emission from the $\gamma$-ray blazar population only accounts for a small fraction of the total astrophysical neutrino flux. We present and discuss recent results on the search for correlations between astrophysical neutrinos and both gamma-ray and radio bright AGN. The IceCube Collaboration has reported high-energy neutrino events that may come from both the radio-loud AGN TXS 0506+056 and the radio-quiet AGN NGC 1068. Other cases of possible associations between high-energy neutrino events and individual blazars were claimed with controversial results. We discuss the properties of these sources together with the different neutrino production mechanisms proposed for those sources. Finally, we outline future prospects in the field, focusing on remaining open questions, the development of upcoming neutrino facilities, and the evolving multi-frequency landscape within the multi-messenger era.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 2 minor

Summary. The manuscript is a review summarizing IceCube observations of high-energy astrophysical neutrinos and their possible associations with Active Galactic Nuclei (AGN). It highlights candidate sources including the radio-loud blazar TXS 0506+056 and the radio-quiet Seyfert galaxy NGC 1068, notes that the gamma-ray blazar population accounts for only a small fraction of the total neutrino flux based on population studies, discusses proposed neutrino production mechanisms, and outlines future prospects with upcoming facilities in the multi-messenger context.

Significance. As a synthesis of recent multi-messenger results, the review provides a useful overview of an active research area, correctly employing cautious language regarding individual source associations and emphasizing the limited blazar contribution. It draws attention to open questions without introducing new claims, derivations, or statistical tests.

minor comments (2)
  1. [Abstract] Abstract: The statement 'We present and discuss recent results on the search for correlations' could be rephrased to explicitly note that the work is a review summarizing published IceCube findings and external population studies rather than reporting new analyses or data.
  2. The manuscript would benefit from a dedicated section or table listing the key IceCube events, their energies, and the specific AGN associations discussed, to improve readability for readers unfamiliar with the cited reports.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript and for recommending acceptance. The referee's summary correctly reflects the scope of the review as a synthesis of IceCube results on AGN-neutrino associations, population constraints, and future prospects.

Circularity Check

0 steps flagged

No significant circularity; review contains no derivations

full rationale

The manuscript is a review summarizing external IceCube reports and population studies on AGN-neutrino associations. It presents no equations, fitted parameters, predictions, or new statistical claims; all statements use cautious language and cite external results. No load-bearing step reduces by construction to inputs, self-citations, or ansatzes. The paper is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

This is a review paper; the abstract introduces no new free parameters, axioms, or invented entities.

pith-pipeline@v0.9.1-grok · 5746 in / 1137 out tokens · 47434 ms · 2026-07-01T02:00:33.351571+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

300 extracted references · 132 canonical work pages · 43 internal anchors

  1. [1]

    G., Abbasi, R., Abdouand, Y., et al

    Aartsen, M. G., Abbasi, R., Abdouand, Y., et al. 2013, Science, 342, 1242856

    2013

  2. [2]

    G., Abraham, K., Ackermann, M, et al

    Aartsen, M. G., Abraham, K., Ackermann, M, et al. 2017, ApJ, 835, 151

    2017

  3. [3]

    Aartsen, M. G. Ackermann, M.; Adams, J., et al. 2017, APh, 92, 30

    2017

  4. [4]

    G., Abbasi, R., Abdouand, Y., et al

    Aartsen, M. G., Abbasi, R., Abdouand, Y., et al. 2018, Science, 361, 147

    2018

  5. [5]

    G., Ackermann, M., Adams, J., et al

    Aartsen, M. G., Ackermann, M., Adams, J., et al. 2018, PhRvD, 98, 062003

    2018

  6. [6]

    G., Ackermann, M., Adams, J., et al

    Aartsen, M. G., Ackermann, M., Adams, J., et al. 2020, PhRvL, 124, 1103

    2020

  7. [7]

    G., Abbasi, R., Ackermann, M., et al

    Aartsen, M. G., Abbasi, R., Ackermann, M., et al. 2021, JPhG, 48f0501

    2021

  8. [8]

    G., Ackermann, M., Adams, J., et al

    Aartsen, M. G., Ackermann, M., Adams, J., et al. 2023, Science, 380, 1338

    2023

  9. [9]

    2021, PhRvD, 104, 2002

    Abbasi, R., Ackermann, M., Adams, J., et al. 2021, PhRvD, 104, 2002

    2021

  10. [10]

    2022, ApJ, 928, 50

    Abbasi, R., Ackermann, M., Adams, J., et al. 2022, ApJ, 928, 50

    2022

  11. [11]

    2022, Science, 378, 538

    Abbasi, R., Ackermann, M., Adams, J., et al. 2022, Science, 378, 538

    2022

  12. [12]

    2023, ApJ, 954, 75

    Abbasi, R., Ackermann, M., Adams, J., et al. 2023, ApJ, 954, 75

    2023

  13. [13]

    2023, ApJS, 269, 25

    Abbasi, R., Ackermann, M., Adams, J., et al. 2023, ApJS, 269, 25

    2023

  14. [14]

    2023, Science, 380, 1338

    Abbasi, R., Ackermann, M., Adams, J., et al. 2023, Science, 380, 1338

    2023

  15. [15]

    2023, ApJ, 951, 45

    Abbasi, R., Ackermann, M., Adams, J., et al. 2023, ApJ, 951, 45

    2023

  16. [16]

    2024, ApJ, 973, 97

    Abbasi, R., Ackermann, M., Adams, J., et al. 2024, ApJ, 973, 97

    2024

  17. [17]

    2025, 988, 141

    Abbasi, R, Ackermann, M., Adams, J., et al. 2025, 988, 141

    2025

  18. [18]

    U., Albert, A., Alfaro, R., et al

    Abeysekara, A. U., Albert, A., Alfaro, R., et al. 2017, ApJ, 843, 39

    2017

  19. [19]

    Biland, A, Brand, K., et al

    Abhir, J. Biland, A, Brand, K., et al. 2025, submitted to ApJ, arXiv:2512.16562

    work page arXiv 2025

  20. [20]

    A., Ansoldi, S., Antonelli, L

    Acciari, V. A., Ansoldi, S., Antonelli, L. A., et al. 2019, ApJ, 883, 135

    2019

  21. [21]

    A., Aniello, T., Ansoldi, S., et al 2022, ApJ, 927, 197

    Acciari, V. A., Aniello, T., Ansoldi, S., et al 2022, ApJ, 927, 197

    2022

  22. [22]

    S., Agudo, I., Samarai, Al., et al

    Acharya, B. S., Agudo, I., Samarai, Al., et al. 2019, World Scientific book

    2019

  23. [23]

    2016, Journal of Physics G: Nuclear and Particle Physics, 43, 8, 084001

    Adrian-Martinez, S., Ageron, M., Aharonian, F., et al. 2016, Journal of Physics G: Nuclear and Particle Physics, 43, 8, 084001

    2016

  24. [24]

    Aiello, S., Albert, A., et al

    Adriani, O. Aiello, S., Albert, A., et al. 2025, ApJL, 984, 2

    2025

  25. [25]

    A., Al Samarai, I., et al

    Ageron, M., Aguilar, J. A., Al Samarai, I., et al. 2011, NIMA, 656, 11

    2011

  26. [26]

    A., Allison, P., Beatty, J

    Aguilar, J. A., Allison, P., Beatty, J. J., et al. 2021, Journal of Instrumentation, 16, P03025

    2021

  27. [27]

    G., Bazer-Bachi, A

    Aharonina, F., Akhperjanian, A. G., Bazer-Bachi, A. R., et al. 2006, A&A, 457, 899

    2006

  28. [28]

    2021, Chin

    Aharonian, F., An, Q., Axikegu, et al. 2021, Chin. Phys. C, 45, 025002

    2021

  29. [29]

    N., Bai, X, et al

    Ahrens, J., Bahcall, J. N., Bai, X, et al. 2004, APh, 20, 507

    2004

  30. [30]

    R., et al

    Aiello, S., Albert A., Alhebsi, A. R., et al. 2025, Science, 638, 376

    2025

  31. [31]

    2021, JCAP, 01, 064

    Albert, A., Andre, M., Anghinolfi, M., et al. 2021, JCAP, 01, 064

    2021

  32. [32]

    A., Antonelli, L

    Aleksic J., Alvarez, E. A., Antonelli, L. A., et al. 2012, APh, 35, 435

    2012

  33. [33]

    A., Avrorin, A

    Allakhverdyan, V. A., Avrorin, A. D., Avrorin, A. V., et al. 2024, MNRAS, 527, 8784

    2024

  34. [34]

    Y., Venturi, T., et al

    An, T., Hong, X. Y., Venturi, T., et al. 2004, A\ A, 421, 389

    2004

  35. [35]

    A., Arcaro, C., et al

    Ansoldi, S., Antonelli, L. A., Arcaro, C., et al. 2018, ApJ, 863, L10 \

    2018

  36. [36]

    Atoyan, A., & Dermer, C. D. 2001, PhRvL, 87, 221102

    2001

  37. [37]

    , Cordier, B., Wei, J

    Atteia, J.-L. , Cordier, B., Wei, J. 2022, IJMPD, 313008

    2022

  38. [38]

    B., Abdo, A

    Atwood, W. B., Abdo, A. A., Ackermann, M., et al. 2009, ApJ, 697, 1071

    2009

  39. [39]

    2015, 800L, 27

    Ajello, M., Gasparrini, D., Sanchez-Conde, M., et al. 2015, 800L, 27

    2015

  40. [40]

    2020, ApJ, 892, 105

    Ajello, M., Angioni, R., Axelsson, M., et al. 2020, ApJ, 892, 105

    2020

  41. [41]

    2022, ApJS, 263, 24

    Ajello, M., Baldini, L., Ballet, J., et al. 2022, ApJS, 263, 24

    2022

  42. [42]

    Becker Tjus, J., Eichmann, B., Halzen, F.; Kheirandish, A.; Saba, S. M

  43. [43]

    2022, ApJ, 941, L25

    Becker Tjus, J., Jaroschewski, I., Ghorbanietemad, A., et al. 2022, ApJ, 941, L25

    2022

  44. [44]

    2023, ApJ, 955, L32

    Bellenghi, C., Padovani, P., Resconi, E., Giommi, P. 2023, ApJ, 955, L32

    2023

  45. [45]

    2014, JInst, 9, P0012

    Biland, A., Bretz, T., Buss, J., et al. 2014, JInst, 9, P0012

    2014

  46. [46]

    2014, Nuclear Physics 3 Proceedings Supplements 256, 9

    Blandford, R., Simeon, P., Yuan, Y. 2014, Nuclear Physics 3 Proceedings Supplements 256, 9

    2014

  47. [47]

    2013, ApJ, 768, 54

    Bottcher, M., Reimer, A., Sweeney, K., Prakash, A. 2013, ApJ, 768, 54

    2013

  48. [48]

    , Bourke, T., Green, J

    Braun, R. , Bourke, T., Green, J. A., et al. 2015, Proceedings of Advancing Astrophysics with the Square Kilometre Array (AASKA14), 174

    2015

  49. [49]

    Buson, S., Tramacere, A., Oswald, L., et al., 2022, ApJ, 933, L43

    2022

  50. [50]

    A., et al

    Caputo, R., Ajello, M., Kierans, C. A., et al. 2022, JATIS, 8, 044003

    2022

  51. [51]

    2015, MNRAS,448, 910

    Cerruti, M.; Zech, A.; Boisson, C., et al. 2015, MNRAS,448, 910

    2015

  52. [52]

    P., Werner, M., Akeson, R., et al

    Crill, B. P., Werner, M., Akeson, R., et al. 2020, Proceedings of the SPIE, 11443E, 0I

    2020

  53. [53]

    2025, Nature Astronomy, 9, 36

    Cruise, M., Guainazzi, M., Aird, J., et al. 2025, Nature Astronomy, 9, 36

    2025

  54. [54]

    S., Barrett, J., Blackburn, L., et al

    Doeleman, S. S., Barrett, J., Blackburn, L., et al. 2023, Galaxies, 11, 10

    2023

  55. [55]

    A., Suvorova, O., Baikal-GVD Collaboration 2021, the Astronomer's Telegram, 15112, 1

    Dzhilkibaev, Z. A., Suvorova, O., Baikal-GVD Collaboration 2021, the Astronomer's Telegram, 15112, 1

    2021

  56. [56]

    2024, A&A, 684, A11

    Eppel, F., Kadler, M., Hessdorfer, J., et al. 2024, A&A, 684, A11

    2024

  57. [57]

    L., & Riley, J

    Fanaroff, B. L., & Riley, J. M. 1974, MNRAS, 167, 31

    1974

  58. [58]

    2017, in International Cosmic Ray Conference, Vol

    Fang, K., Alvarez-Muniz, J., Alves Batista, R., et al. 2017, in International Cosmic Ray Conference, Vol. 301, 35th International Cosmic Ray Conference (ICRC2017), 996

    2017

  59. [59]

    S., Halzen, F

    Fang, K., Gallagher, J. S., Halzen, F. 2022, ApJ, 933, 109

    2022

  60. [60]

    Fang, K., Lopez Rodriguez, E., Halzen, F., Gallagher, J. S. 2023, ApJ, 956, 8

    2023

  61. [61]

    2022, ATel, 15290, 1

    Filippini, F., Illuminati, G., Heijboer, A., et al. 2022, ATel, 15290, 1

    2022

  62. [62]

    G., Petropoulou, M., Comisso, L., et al

    Fiorillo, F. G., Petropoulou, M., Comisso, L., et al. 2024, ApJ, 961, L14

    2024

  63. [63]

    G., Testagrossa, F., Petropoulou

    Fiorillo, F. G., Testagrossa, F., Petropoulou. M., Winter, W. 2025, ApJ, 986, 1

    2025

  64. [64]

    T., Honscheid, K., et al

    Flaugher, B., Diehl, H. T., Honscheid, K., et al. 2015, ApJ, 150, 150

    2015

  65. [65]

    2020, ApJ, 893, 162

    Franckowiak, A., Garrappa, S., Paliya, V., et al. 2020, ApJ, 893, 162

    2020

  66. [66]

    F., Baum, S

    Gallimore, J. F., Baum, S. A., O?Dea, C. P. 2004, ApJ, 613, 794

    2004

  67. [67]

    Gao, S., Pohl, M., & Winter, W., 2017, ApJ, 843, 109

    2017

  68. [68]

    Garcia-Burillo, S., Combes, F., Ramos Almeida, C. et al. 2016, ApJL, 823, L12

    2016

  69. [69]

    Garcia-Burillo, S., Combes, F., Ramos Almeida, C. et al. 2019, A&A, 632, A61

    2019

  70. [70]

    2019, ApJ, 880, 103

    Garrappa, S., Buson, S., Franckoviak, A., et al. 2019, ApJ, 880, 103

    2019

  71. [71]

    Garrappa, S., Buson, S., 2020, , GCN, 26669

    2020

  72. [72]

    2004, ApJ, 611, 1005

    Gehrels, N., Chincarini, G., Giommi, P., et al. 2004, ApJ, 611, 1005

    2004

  73. [73]

    2005, A&A, 432, 401

    Ghisellini, G., Tavecchio, F., Chiaberge, M. 2005, A&A, 432, 401

    2005

  74. [74]

    2009, MNRAS, 397, 985

    Ghisellini, G., Tavecchio, F. 2009, MNRAS, 397, 985

    2009

  75. [75]

    2011, MNRAS, 414, 2674

    Ghisellini, G., Tavecchio, F., Foschini, L., Ghirlanda, G. 2011, MNRAS, 414, 2674

    2011

  76. [76]

    2017, MNRAS, 469, 255

    Ghisellini, G., Righi, C., Costamante, L., Tavecchio, F. 2017, MNRAS, 469, 255

    2017

  77. [77]

    E., Kim, D

    Gianolli, V. E., Kim, D. E., Bianchi, S., et al. 2023, MNRAS 523, 4468

    2023

  78. [78]

    2020, A&A, 640, L9

    Giommi, P., Padovani, P., Oikonomou, F., et al. 2020, A&A, 640, L9

    2020

  79. [79]

    1960, Anual Review Nuclear Science, 10, 63

    Greisen, K. 1960, Anual Review Nuclear Science, 10, 63

    1960

  80. [80]

    A., Craig, W

    Harrison, F. A., Craig, W. W., Christensen, F. E., et al. 2013, ApJ, 770, 103

    2013

Showing first 80 references.