Speaker
Description
The High Altitude Water Cherenkov (HAWC) Observatory is a wide-field water Cherenkov detector (WCD) that continuously monitors the gamma-ray sky in the energy range from hundreds of GeV to beyond 100 TeV. After nine years of observations, spanning from 2015 to 2024, HAWC provides measurements on four radio galaxies in the northern hemisphere known to emit at very-high-energy (VHE) gamma rays. Among these sources, M87 is significantly detected at the 7$\sigma$ level, representing the only confirmed VHE detection in the sample. Although 3C 264, NGC 1275, and IC 310 do not yet reach the 5$\sigma$ detection threshold, the derived upper limits constitute the first constraints on their VHE emission obtained with a WCD. The multi-wavelength spectral energy distributions (SEDs) of these radio galaxies have traditionally been described using the standard synchrotron self-Compton (SSC) model. However, the inclusion of HAWC measurements reveals that a single-zone SSC scenario is insufficient to reproduce the broadband emission. In this work, we explore more complex models, including a leptonic two-zone SSC scenario, and a hadronic model based on pion decay, to describe the SEDs of these sources from radio to TeV energies. We further discuss the physical implications of these models for particle acceleration and emission processes in radio galaxies.
This work was supported by UNAM-PAPIIT IG100726 y SECIHTI LNC-2023-117