Observations of very high energy gamma-ray emission from AGNs with the ground-based EAS arrays

TL;DR

This paper reviews the contributions of ground-based EAS arrays in observing very high energy gamma-ray emissions from AGNs, highlighting their role in long-term monitoring and the potential of future projects like LHAASO.

Contribution

It summarizes past findings and discusses how next-generation EAS arrays will significantly enhance gamma-ray observations and understanding of AGN physics.

Findings

EAS arrays have monitored AGNs like Mrk 421 and Mrk 501 over long periods.

Current arrays operate above 3 TeV and 0.3 TeV energies.

LHAASO will increase sensitivity by 30 times and cover 40 GeV to 1 PeV energies.

Abstract

The ground-based EAS array is usually operated with a high duty cycle (> 90%) and a large field of view (~2 sr), which can continuously monitor the sky. It is essential and irreplaceable to understand the gamma-ray emission mechanism and intrinsic physics progress of the variable source AGN. The EAS arrays, AS-r experiment (since 1990) and ARGO-YBJ experiment (since 2007), have continuously monitored the northern sky at energies above 3 TeV and 0.3 TeV, respectively. They have made substantial contributions for long-term monitoring of Mrk 421 and Mrk 501. In this paper, we will review the results obtained by the EAS arrays. The next generation of EAS array, LHAASO project, will boost the sensitivity of current EAS array at least up to 30 times with a much wider energy range from 40 GeV to 1 PeV. Beside increasing the number of VHE gamma-ray sources, it will guide us look sight into the properties of jet, and throw light on the determining of the EBL, intergalactic magnetic fields, and the validity of the Lorentz Invariance.