High-resolution molecular line observations of active galaxies

TL;DR

This paper reviews high-resolution molecular line observations of active galaxies, emphasizing how mm-interferometry reveals gas distribution, kinematics, and chemistry to understand AGN fueling and feedback processes.

Contribution

It provides a comprehensive review of recent molecular line mapping techniques and findings in active galaxies, highlighting their role in studying AGN feeding and feedback mechanisms.

Findings

CO maps reveal gas distribution and dynamics in circumnuclear disks.

Molecular tracers show chemical differentiation in galaxy centers.

Active galaxies serve as local templates for distant galaxy studies.

Abstract

The study of the content, distribution and kinematics of interstellar gas is a key to understand the origin and maintenance of both starburst and nuclear (AGN) activity in galaxies. The processes involved in AGN fueling encompass a wide range of scales, both spatial and temporal, which have to be studied. Probing the gas flow from the outer disk down to the central engine of an AGN host, requires the use of specific tracers of the interstellar medium adapted to follow the change of phase of the gas as a function of radius. Current mm-interferometers can provide a sharp view of the distribution and kinematics of molecular gas in the circumnuclear disks of galaxies through extensive CO line mapping. As such, CO maps are an essential tool to study AGN feeding mechanisms in the local universe. This is the scientific driver of the NUclei of GAlaxies (NUGA) survey, whose latest results are here reviewed. On the other hand, the use of specific molecular tracers of the dense gas phase can probe the feedback influence of activity on the chemistry and energy balance/redistribution in the interstellar medium of nearby galaxies. Millimeter interferometers are able to unveil the strong chemical differentiation present in the molecular gas disks of nearby starbursts and AGNs. Nearby active galaxies can be used as local templates to address the study of more distant galaxies where both star formation and AGN activity are deeply embedded.