The AGNS and their host galaxies as seen in the mid-infrared

Author: Laurent O.  

Publisher: Springer Publishing Company

ISSN: 0004-640X

Source: Astrophysics and Space Science, Vol.266, Iss.1-2, 1999-01, pp. : 175-180

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Abstract

We present a new diagnostic diagram based on ISOCAM spectra (5-16 μm) to distinguish the emission induced by the active galactic nucleus (AGN) from that associated with the star formation activity. This diagnostic based on the mid-IR continuum and the Unidentified Infrared Band (UIB) intensity allows us to estimate the relative importance of the three components (HII regions, diffuse/photo-dissociation regions (PDRs), and AGN) contained in galaxy mid-infrared emission. In AGN spectra, we confirm the absence of UIBs presumably photodissociated by the X-UV radiation field. In addition, a non-negligible continuum below 9 μm commonly associated with emission from hot dust is present in AGNs. A diagnostic diagram derived from these two results can be used for detecting obscured AGNs embedded in a large concentration of dust.