we propose deep imaging of two collisonal ring galaxies in 4 mid-ir bands of isocam in order to map the distribution of dust in these galaxies. ring galaxies are believed to be formed when a small companion galaxy plunges through the center of a rotating disk system, driving radially expanding waves into the disk. these waves have been shown to trigger star formation as they pass through the disk. ring galaxies, through their special dynamical properties are therefore remarkable laboratories for studying the evolution of young massive star clusters formed in collisions. ring galaxies exhibit unusually high local star formation rates comparable to those seen in the nuclei of starburst galaxies. unlike these more complicated cousins, the ring starbursts have a well defined history dictated by the propagation velocity of the ring. typical rings expand through the disk in a few hundred million years leaving a trail of evolving star clusters in their wake. this effect, which was predicted by numerical models, has been recently observed to produce unusually large radial color gradients within the rings. our observations will provide the first high sensitivity images of two molecular-rich classical ring galaxies, ngc 985 and viizw466. the observations will allow for the first time the detailed distribution of dust to be imaged and compared with co maps, radio continuum, optical and near ir images of the systems. we expect to detect dust not only within the bright star forming rings, but possibly also from inside the ring, where in at least one case, large quantities of molecules reside. attempts to detect the rings from the ground at 5 microns failed because of the relatively faint nature of the emission. iso is the ideal instrument for our project.
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
