THE MID-IR VIEW OF INTERACTING GALAXIES V. CHARMANDARIS Observatoire de Paris - DEMIRM, France O. LAURENT, I.F. MIRABEL, P. GALLAIS, M. SAUVAGE, L. VIGROUX AND C. CESARSKY CEA/DSM/DAPNIA, Service d’Astrophysique, France AND D. TRAN MPI f¨ ur extraterrestriche Physik, Garching, Germany Abstract. In this paper, we present ISOCAM mid-IR broad band images and spectra of three well known interacting galaxies. These are the prototypical ultraluminous IR galaxy Arp 220, and NGC 6240, which are classified as major mergers resulting from a collision of two disk galaxies of approxim- ately equal mass, and the prime example of collisional ring galaxies, the Cartwheel. Our observations provide a new powerful tool and shed some more light to the properties of the hot dust and star formation in interacting galaxies. Key words: galaxy – mid-infrared – starburst 1. Introduction It is well accepted that galaxy interactions frequently lead to merging, and play a fundamental role in the formation and morphological evolution of galaxies (Toomre & Toomre, 1972). Multi-wavelength studies of a class of “infrared luminous galaxies” (L bol ≥ 10 11 L ⊙ ), which emit more energy in the infrared (5-500 μm) than in all other wavelengths combined (see review by Sanders & Mirabel 1996), indicate that most of them reveal strong evidence of merging. Astrophysics and Space Science is the original source of publication of this article. It is recommended that this article is cited as: Astrophysics and Space Science 266: 99–104, 1999. c 1999 Kluwer Academic Publishers. Printed in the Netherlands.