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Astron. Astrophys. 325, L21-L24

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Letter to the Editor

Infrared spectral energy distributions
of the interacting galaxies Arp 244, NGC 6240, and Arp 220*

Ulrich Klaas1,2 and Martin Haas1, and Ingolf Heinrichsen3,2, and Bernhard Schulz2

1Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany,
2ISO Science Operations Centre, Astrophysics Division, Space Science Department of ESA, Villafranca, P.O. Box 50727,
E-28080 Madrid, Spain
3Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany

Received 3 June 1997 / Accepted 26 June 1997


For the luminous galaxies Arp 244, NGC 6240 and Arp 220 detailed infrared spectral energy distributions between 3 and 200 µm obtained with ISOPHOT are presented. The maximum of the infrared energy distribution can now clearly be determined. The SEDs can be well represented by cold dust emission with temperatures of 30-50 K which by far dominates the luminosity. In addition, a second warm dust component is present with temperatures of 120-160 K. The infrared luminosities derived from the ISOPHOT data agree, within the errors, with the extrapolated IRAS 8-1000µm luminosities. The cold component of Arp 244 shows similarities to HII regions in normal galaxies, while NGC 6240 and Arp 220 have huge dust masses heated up to considerably higher temperatures. We discuss the observations in the context of heating by starbursts and conversion of mechanical energy from collision or outflow.

Key words: Infrared: galaxies, Galaxies: photometry, fundamental parameters, starburst, individual: Arp 244, NGC6240, Arp 220

*Based on observations with 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: U. Klaas (uklaas@iso.vilspa.esa.es)

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998