Directional Association of TeV to PeV Astrophysical Neutrinos with Radio Blazars

Abstract

Recently we have shown that high-energy neutrinos above 200 TeV detected by IceCube are produced within several parsecs in the central regions of radio-bright blazars, that is active galactic nuclei with jets pointing toward us. To independently test this result and extend the analysis to a wider energy range, we use public data for all neutrino energies from seven years of IceCube observations. The IceCube point-source likelihood map is analyzed against the positions of blazars from a statistically complete sample selected according to their compact radio flux density. The latter analysis delivers a 3.0σ significance, with the combined post-trial significance of both studies being 4.1σ. The correlation is driven by a large number of blazars. Together with fainter but physically similar sources not included in the sample, they may explain the entire IceCube astrophysical neutrino flux as derived from muon-track analyses. The neutrinos can be produced in interactions of relativistic protons with X-ray self-Compton photons in parsec-scale blazar jets.

Neutrino Telescope in Lake Baikal: Present and Nearest Future

“…Recent works have shown that high-energy neutrinos of TeV to PeV energies are produced in active galactic nuclei. Specifically, within several parsecs from the supermassive black hole of radio-bright blazars with jets pointing towards us [22,23]. We base the following analysis on those conclusions, and present our preliminary results regarding the blazar-neutrino connection.…”

Testing the AGN Radio and Neutrino correlation using the MOJAVE catalog and 10 years of IceCube Data

“…Multiple follow-up analyses have been launched in order to help us understand if AGN are responsible for the production of these astrophysical neutrinos, and how they are produced. Multi-messenger analyses like [3][4][5][6][7] which study the correlation of IceCube neutrinos with the observed electromagnetic radiation at different wavelengths from AGN help us understand the processes that could give rise to neutrinos in AGN.…”

“…One of the theories that could predict the production of high-energy neutrinos in AGN is discussed recently by an analysis reported by [4,5] which looks into a correlation between the seven-year public IceCube data and Very-Long-Baseline radio Interferometry (VLBI) selected AGN. Production of high-energy neutrinos can occur via , hadronic (nucleon-nucleon) or photohadronic (nucleon-photon) interactions in AGN [4,8].…”

“…In the bright central parsecs of AGN, observable in the radio band, interactions are generally suppressed with respect to interactions [9,10]. In [5] it is argued that, if interactions are the cause of high-energy neutrinos then the gamma rays, produced in these photohadronic processes alongside with neutrinos, will interact with the same target photons to produce electron-positron pairs which will lead to a chain of processes resulting in gamma rays without enough energy to undergo pair production. This theory, which is also discussed by [6], can serve as a possible explanation for the lack of high energy gamma-ray (as observed by Fermi-LAT) and neutrino correlation in AGN and may hint towards a correlation with lower energy gamma-rays in the keV to GeV regime.…”

“…Although the theories proposed by analyses like [4][5][6] are very promising, they are based on hints of radio-neutrino correlation with marginal statistical significance due to the limited data available. It makes it necessary to follow up with enough statistical power to test the authenticity of this correlation.…”