Aromatic Features in AGN: Star-Forming Infrared Luminosity Function of AGN Host Galaxies

TL;DR

This study investigates aromatic features in AGN to understand the star formation activity in their host galaxies, revealing how nuclear activity influences star-forming infrared luminosity functions across different AGN types.

Contribution

It provides new insights into the relationship between AGN nuclear activity and star formation by analyzing aromatic features and deriving star-forming luminosity functions for various AGN types.

Findings

Star formation contributes about 25% to far-IR emission in AGN.

Star-forming luminosity functions are flatter than in field galaxies.

Different AGN types show varying levels of star formation activity.

Abstract

We describe observations of aromatic features at 7.7 and 11.3 um in AGN of three types including PG, 2MASS and 3CR objects. The feature has been demonstrated to originate predominantly from star formation. Based on the aromatic-derived star forming luminosity, we find that the far-IR emission of AGN can be dominated by either star formation or nuclear emission; the average contribution from star formation is around 25% at 70 and 160 um. The star-forming infrared luminosity functions of the three types of AGN are flatter than that of field galaxies, implying nuclear activity and star formation tend to be enhanced together. The star-forming luminosity function is also a function of the strength of nuclear activity from normal galaxies to the bright quasars, with luminosity functions becoming flatter for more intense nuclear activity. Different types of AGN show different distributions in the level of star formation activity, with 2MASS> PG> 3CR star formation rates.