The AGNS and their host galaxies as seen in the mid-infrared
Cesarsky, C.; Sauvage, M.; Vigroux, L.; Charmandaris, V.; Mirabel, I. F.; Gallais, P.; Laurent, O.
France
Abstract
We present a new diagnostic diagram based on ISOCAMspectra (5-16 μm) to distinguish the emission inducedby the active galactic nucleus (AGN) from that associated with thestar formation activity. This diagnostic based on the mid-IRcontinuum and the Unidentified Infrared Band (UIB) intensity allowsus to estimate the relative importance of the three components (HIIregions, diffuse/photo-dissociation regions (PDRs), and AGN) contained ingalaxy mid-infrared emission. In AGN spectra, we confirm the absenceof UIBs presumably photodissociated by the X-UV radiation field. Inaddition, a non-negligible continuum below 9 μm commonlyassociated with emission from hot dust is present in AGNs. Adiagnostic diagram derived from these two results can be used fordetecting obscured AGNs embedded in a large concentration of dust.