The Past and Future of Mid-Infrared Studies of AGN

TL;DR

Mid-infrared studies of AGN are vital for understanding their properties, obscuring structures, and impact on galaxy evolution, with recent advances driven by space and ground-based observations and future prospects with JWST.

Contribution

This review summarizes the development and key findings of mid-infrared AGN studies, highlighting technological progress and future opportunities with JWST.

Findings

Mid-IR observations reveal obscuring structures around AGN.

Mid-IR features probe multiple components of the ISM.

Mid-IR studies contribute to understanding galaxy-SMBH co-evolution.

Abstract

Observational studies of AGN in the mid-infrared regime are crucial to our understanding of AGN and their role in the evolution of galaxies. Mid-IR-based selection of AGN is complementary to more traditional techniques allowing for a more complete census of AGN activity across cosmic time. Mid-IR observations including time variability and spatially resolved imaging have given us unique insights into the nature of the obscuring structures around AGN. The wealth of fine structure, molecular, and dust features in the mid-IR allow us to simultaneously probe multiple components of the ISM allowing us to explore in detail the impact on the host galaxy by the presence of an AGN -- a crucial step toward understanding galaxy-SMBH co-evolution. This review gives a broad overview of this wide range of studies. It also aims to show the evolution of this field starting with its nascency in the 1960s, through major advances thanks to several generations of space-based and ground-based facilities, as well as the promise of upcoming facilities such as the {\sl James Webb Space Telescope (JWST)}.