The Mid-Infrared Spectra of Interacting Galaxies: From ISO to SIRTF
  We present mid-infrared (5--16micron) images and spectra of a sequence of interacting galaxies, observed by ISOCAM. The galaxies were selected as being at progressive stages in the time evolution of a merging event, following what is known as Toomre's ``merger sequence'', and having no detected contribution from an active galactic nucleus (AGN) in their mid-infrared spectrum. To trace the intensity of the global star formation in those galaxies, we use the ratio of the 15micron to 7micron flux. Our analysis indicates that this ratio increases from ~1 to ~5 as galaxies move from the pre-starburst to the merging/starburst phase only to decrease to ~1 again in the post-starburst phase of the evolved merger remnants. Moreover, we find that the variation of this ratio is well correlated with the one of the IRAS 25/12 and 60/100 flux ratios. The potential to test and improve upon these results using the Infrared Spectrograph (IRS) on board SIRTF is discussed. 
V. Charmandaris (1), O.Laurent (2), I.F. Mirabel (3), P. Gallais (3),   J. Houck, (1) ((1)Cornell University, USA, (2) MPE, ...