# A survey of Active Galaxies with the HAWC Gamma-ray Observatory

## TL;DR

This paper presents a survey of active galactic nuclei using three years of HAWC gamma-ray data, confirming detections of Mrk 421 and Mrk 501 and setting flux limits for others, advancing understanding of TeV gamma-ray sources.

## Contribution

It provides the first deep, unbiased survey of active galactic nuclei at TeV energies with HAWC, confirming known sources and establishing new flux limits.

## Key findings

- Confirmed TeV emission from Mrk 421 and Mrk 501.
- Set flux upper limits for other AGN in the sample.
- Demonstrated HAWC's capability for long-term TeV sky surveys.

## Abstract

The High Altitude Water Cherenkov Gamma-Ray Observatory has been accumulating a progressively deeper exposure of the TeV sky since its inauguration in March 2015. Located at geographical latitude $+19^\circ$N, HAWC has been able to perform a deep and unbiased survey of two thirds of the sky. We analyzed three years of HAWC data searching for long term persistent emission from a redshift limited ($z\leq 0.3$) sample of active galactic nuclei drawn from the {\it Fermi}-LAT 3FHL catalog. The HAWC dataset confirms the high significance detection of the two nearest BL Lac objects, \mbox{Mrk 421} and \mbox{Mrk 501}, and sets limits for the rest of the sample, down to integrated photon fluxes of order $N(>0.5~{\rm TeV})\lesssim 10^{-12}\,\rm cm^{-2}s^{-1}$. We present and discuss some of the results of this survey, focusing on individual objects of particular interest.