Leha-paris Code Simulations Link Blazar Emissions to 290 TeV Neutrino Detection in September 2017

Identifying the sources of high-energy cosmic neutrinos remains a fundamental challenge in astrophysics, but recent work offers new insights into these elusive particles. Francesco Carenini from Università di Bologna and Matteo Cerruti from Université Paris Cité, along with their colleagues, investigate the connection between blazars and neutrino emissions using advanced simulations. Their research builds on the discovery linking the blazar TXS 0506+056 to a high-energy neutrino detected in 2017, and focuses on developing a methodology to predict neutrino fluxes from a wider class of blazars known as High-frequency-peaked BL Lacs (HBLs). By employing the LeHa-Paris code to model proton interactions and radiative processes, the team generates neutrino emission models for a selection of HBLs, offering a crucial step towards identifying the astrophysical sources responsible for these high-energy particles.

This discovery prompted scientists to explore the theoretical link between photon and neutrino emissions, leading to sophisticated simulations of proton-photon interactions within blazars to predict neutrino spectra.

Blazar Neutrino Emission Modeled with LeHa-Paris

Scientists developed a sophisticated methodology to model neutrino emissions from blazars, leveraging the LeHa-Paris code to compute both leptonic and hadronic contributions to spectral energy distributions. The study began with detailed modeling of PKS 2155-304, a well-studied HBL known for its extreme variability and extensive multi-wavelength observations, establishing a foundation for generating neutrino flux templates applicable to all HBLs. The LeHa-Paris code functions as a steady-state numerical model, calculating photon and neutrino emission from relativistic electrons and protons within a spherical emitting region inside a relativistic jet.

Researchers adopted a one-zone emission model, simplifying the complex jet structure by assuming all emission originates from a single spherical region characterized by a radius, magnetic field strength, and Doppler factor. This approach effectively reproduces observed broad-band spectral energy distributions and variability patterns in blazars by attributing emission to this single zone. The primary electron population is described by a broken power-law distribution, incorporating internal absorption due to gamma-gamma pair production. To model the hadronic component, scientists calculated proton synchrotron radiation and simulated proton-photon interactions, considering synchrotron photons from both primary electrons and protons, as well as synchrotron self-Compton (SSC) photons as target fields.

The code computes steady-state distributions for secondary leptons resulting from these interactions, accounting for injection, synchrotron and inverse Compton cooling, and adiabatic losses. This innovative approach promises to significantly advance understanding of blazars as potential sources of high-energy cosmic neutrinos.

Blazar Neutrino Emission Modeled for PKS 2155-304

Scientists have achieved a significant breakthrough in understanding high-energy neutrino emissions from blazars, specifically by developing detailed models for PKS 2155-304, a well-studied High-frequency-peaked BL Lacertae object. The team meticulously optimized model parameters to reproduce observed electromagnetic spectra, exploring a wide range of values for electron and proton normalization, spectral indices, magnetic field strength, and emission region size. They established specific ranges for proton normalization based on the maximum proton energy, enabling effective exploration of the parameter space.

The optimization process involved evaluating numerous scenarios using a statistical method, discarding models that did not align with observed radio data or exhibited excessive jet luminosity. Results demonstrate that the best-fit model for PKS 2155-304 requires a proton acceleration mechanism with a specific spectral index, resulting in a larger emission region and a less intense magnetic field compared to previous claims. The optimized model achieves a strong fit to the observed data and predicts a peak in the all-flavor neutrino spectrum, providing a specific prediction for future neutrino observations. This work establishes a robust framework for modeling neutrino emission from HBLs and offers a pathway to identifying additional blazar neutrino sources, advancing our understanding of the most energetic phenomena in the universe.

HBL Neutrino Emission Models Confirmed and Extended

This research presents a methodology for modelling neutrino emission from blazars, a type of active galactic nucleus, and extends these models to the broader class of High-frequency-peaked BL Lacertae objects, or HBLs. The resulting neutrino spectra are consistent with those derived from scaling existing models based on the blazar TXS 0506+056, demonstrating the robustness of the approach. These models allow researchers to predict the expected neutrino flux from HBLs, which is crucial for interpreting data from neutrino telescopes.

The agreement between modelled fluxes and rescaled templates, particularly at energies above one PeV, suggests that these studies are highly relevant for current and future neutrino observations. The authors propose integrating these models into stacking analyses with data from next-generation telescopes like KM3NeT/ARCA to improve the identification of high-energy neutrino sources. This work represents a significant step towards understanding the origin of astrophysical neutrinos and identifying the blazars that contribute to the observed neutrino background.