Contribution to the 'FIRSED2000' conference, eds Barthel, van Bemmel and Wilkes.

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Ilse van Bemmel

European Southern Observatory, Karl-Schwarzschild-Str. 2, D–85748 Garching
Kapteyn Astronomical Institute, P.O.Box 800, NL–9700 AV Groningen

Abstract: In this paper I discuss the issue of the so-called 25 µm–peakers, which were discovered with IRAS, and consist almost solely of broad-line radio galaxies. I find that this peak is caused by the absence of colder dust that emits at 60 µm and not by an excess of hot dust, as suggested by the name. On optical images, the 25 µm peakers show a lack of extended dust. The peakers are consistent with being in a later evolutionary stage, in which all the extended dust has been formed into stars and the dust torus is smaller. If the 60 µm dust is heated by stars, there might be a correlation between the star-formation rate and the power of the AGN.

Keywords : galaxies: active galaxies: infrared quasars: infrared galaxies: ISM

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