Monitoring radio galaxies at TeV energies with HAWC

TL;DR

This paper utilizes the HAWC observatory's wide field of view to monitor radio galaxies at TeV energies, providing upper limits and light curves over three years, to probe VHE emission processes in AGN jets.

Contribution

It presents the first systematic search for TeV gamma rays from radio galaxies using HAWC, establishing upper limits and analyzing their variability over three years.

Findings

No significant TeV gamma-ray excess detected from the three radio galaxies.

Upper limits on TeV emission established for M87, NGC 1275, and 3C 264.

Light curves over three years show no strong variability.

Abstract

With an instantaneous field of view of 2 sr and a duty cycle > 95%, the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is a perfect instrument for monitoring variable TeV sources. Because radio galaxies are a type of Active Galactic Nuclei (AGN) with their jets misaligned with respect to our line of sight, they may help us to probe the physics of very-high-energy (VHE) emission processes in these objects. Three out of four radio galaxies that have been detected at TeV energies by other facilities are located within the field of view of the HAWC Observatory: M87, NGC 1275, and 3C 264. A search for TeV gamma rays at their locations yields no statistically significant excess of counts. We present corresponding upper limits for each radio galaxy and light curves covering 3 years of data taken with HAWC.