The role of dissipation distance on reconnection-driven multi-messenger signals from blazar jets

TL;DR

This study models how the location of magnetic reconnection in blazar jets influences multi-messenger signals, revealing different emission regimes and identifying conditions for efficient neutrino production.

Contribution

It generalizes previous models by self-consistently linking jet properties and emission characteristics across different distances from the SMBH, incorporating multi-messenger predictions.

Findings

Synchrotron and SSC dominate near the SMBH with high magnetization.

External Compton processes are significant near the broad-line region.

Neutrino production peaks upstream of the BLR with hard proton spectra.

Abstract

Blazars are characterized by relativistic jets that are closely aligned with our line of sight. This results in relativistic beaming, making blazars among the most luminous extragalactic sources across the electromagnetic spectrum, from radio waves to gamma-rays and, potentially, in high-energy neutrinos. We present a comprehensive study of multi-messenger emission from blazar jets powered by magnetic reconnection occurring at varying distances from the supermassive black hole (SMBH). By generalizing previous models, we explore how the emission characteristics depend self-consistently on the spatial evolution of key jet properties, including magnetization, bulk Lorentz factor, and external photon fields (accretion disc, broad-line region, and dusty torus). Using numerical simulations, we examined the impact of the initial jet magnetization, particle acceleration efficiency, jet-to-accretion power ratio, and mass accretion rate on the broadband photon spectra and neutrino emission. Our findings reveal distinct emission regimes characterized by different dominant radiative processes: synchrotron and synchrotron self-Compton dominate closer to the SMBH where magnetization is high, while external Compton (EC) processes become significant near the broad-line region (BLR). Neutrino production efficiency is highest upstream of the BLR, driven by enhanced photon target densities from synchrotron and external photons available for photopion interactions, whereas the proton particle distribution is hard. Our model predictions are compared with observations of gamma-ray luminosities and synchrotron peak energies of Fermi-detected blazars, highlighting magnetic reconnection as a potential mechanism driving both electromagnetic and neutrino emissions in astrophysical jets.