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Astron. Astrophys. 354, 453-466 (2000)


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Dust in PG quasars as seen by ISO *

M. Haas 1, S.A.H. Müller 1,2, R. Chini 2, K. Meisenheimer 1, U. Klaas 1, D. Lemke 1, E. Kreysa 3 and M. Camenzind 4

1 Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
2 Astronomisches Institut, Universität Bochum, 44780 Bochum, Germany
3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
4 Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany

Received 18 August 1999 / Accepted 9 December 1999

Abstract

Infrared to millimeter spectral energy distributions (SEDs) have been obtained for a random sample of 17 Palomar Green quasars. The observations were carried out between 4.8 and 200 µm with ISO and supplemented for ten sources with IRAM at 1.3 mm. Eight sources were detected in the far infrared for the first time. The SEDs provide evidence for considerable dust emission and do not support the existence of dust-free, naked quasars. The SEDs resemble those of warm ultraluminous infrared galaxies (ULIRGs). The SEDs show a variety of shapes (power-law, mid-infrared dominated, and far-infrared dominated), suggesting the influence of different heating mechanisms. The mid- and far-infrared luminosities are correlated, suggesting a dependence between the heating mechanisms. The role of AGNs and starbursts for the dust heating is discussed, as well as the link between general ULIRGs and dust-enshrouded quasars.

Key words: galaxies: fundamental parameters – galaxies: photometry – galaxies: quasars: general – infrared: galaxies

* Based on observations with the Infrared Space Observatory ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Send offprint requests to: Martin Haas (haas@mpia-hd.mpg.de)

© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000

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