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.Comment: Accepted for publication in ApJ, 24 pages, 13 figure
