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

June 1998 • 1998A&A...334L..73A

Authors • Aussel, H. • Gerin, M. • Boulanger, F. • Desert, F. X. • Casoli, F. • Cutri, R. M. • Signore, M.

Abstract • We report the detections of the hyperluminous galaxy IRAS F15307 +3252 at z = 0.93 and of the Cloverleaf quasar, H 1413+117 at z = 2.56, in the mid infrared using ISOCAM. The spectrum near 10 microns (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 microns observed wavelength) is 8 x 10(45) erg s(-1) (q_0 = 0.5, H_0 = 75 km s(-1) Mpc(-1) ). This represents 10% of the total infrared emission from 5 to 200 microns (7.5 x 10(46) 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, =~ 1000 K. 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 5/sqrt (m) pc for the Cloverleaf where m is the magnification factor. 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.

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Roc Cutri

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