ISO observations and models of galaxies with hidden broad line regions

¹ School of Computer Science and Engineering, Cyprus College, 6 Diogenes Street, Engomi, 1516 Nicosia, Cyprus e-mail: efstathi@cycollege.ac.cy
² European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching b. München, Germany

Received: 6 September 2004
Accepted: 31 March 2005

Abstract

We present ISO mid-infrared spectrophotometry and far-infrared photometry of galaxies with Hidden Broad Line Regions (HBLR). We also present radiative transfer models of their spectral energy distributions which enable us to separate the contributions from the dusty disc of the AGN and the dusty starbursts. We find that the combination of tapered discs (discs whose thickness increases with distance from the central source in the inner part but stays constant in the outer part) and starbursts provide good fits to the data. The tapered discs dominate in the mid-infrared part of the spectrum and the starbursts in the far-infrared. After correcting the AGN luminosity for anisotropic emission we find that the ratio of the AGN luminosity to the starburst luminosity, , ranges from about unity for IRAS 14454-4343 to about 13 for IRAS 01475-0740. Our results suggest that the warm IRAS colours of HBLR are due to the relatively high . Our fits are consistent with the unified model and the idea that the infrared emission of AGN is dominated by a dusty disc in the mid-infrared and starbursts in the far-infrared.