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Astron. Astrophys. 334, L73-L76 (1998)

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Letter to the Editor

The mid infrared spectrum of the hyperluminous galaxies IRAS F15307+3252 and the Cloverleaf *

H. Aussel 1, M. Gerin 2, 3, F. Boulanger 4, F.X. Désert 5, F. Casoli 3, R.M. Cutri 6 and M. Signore 3

1 DAPNIA, Service d'Astrophysique, CEA/Saclay, Ormes des Merisiers, F-91191 Gif-sur-Yvette Cedex, France
2 Radioastronomie, Ecole Normale Supérieure, 24 rue Lhomond, URA 336 du CNRS, F-75231 Paris Cedex 05, France
3 DEMIRM, Observatoire de Paris, 61 avenue de l'Observatoire, URA 336 du CNRS, F-75014 Paris, France
4 Institut d'Astrophysique Spatiale, Bât 121, Université Paris XI, F-91405 Orsay Cedex, France
5 Observatoire de Grenoble, Domaine Universitaire, B.P. 53, F-38041 Grenoble Cedex 09, France
6 IPAC, California Institute of Technology, MS 100-22, Pasadena, CA 91125, USA

Received 18 March 1998 / Accepted 21 April 1998

Abstract

We report the detections of the hyperluminous galaxy IRAS F15307 +3252 at [FORMULA] and of the Cloverleaf quasar, H 1413+117 at [FORMULA], in the mid infrared using ISOCAM. The spectrum near 10 µm (observed wavelength) joins smoothly with the data taken from the ground or with the IRAS satellite. We have detected none of the infrared features attributed to PAHs. For F15307 +3252, the mid-IR emission (9-16 µm observed wavelength) is [FORMULA] erg s-1 ([FORMULA], H0 = 75 km s-1 Mpc-1). This represents 10% of the total infrared emission from 5 to 200 µm ([FORMULA] erg s-1). The shape of the mid-IR spectrum can be fitted by the emission of warm dust grains at a temperature of about 400 K. For the Cloverleaf QSO, H 1413+117, the grain temperature is even larger, [FORMULA]. This intense near infrared emission can be used to put a lower limit on the size of the emitting regions of 5.7 pc for F15307 +3252 and [FORMULA] pc for the Cloverleaf where m is the magnification factor.

Key words: galaxies: active – ISM: dust – galaxies: individual: F15307 +3252 – galaxies: individual: H 1413+117

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

Send offprint requests to: M. Gerin

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© European Southern Observatory (ESO) 1998

Online publication: June 2, 1998

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