High-Resolution Mid-Infrared Imaging of Infrared-Luminous Starburst Galaxies

Observations for seven infrared luminous starburst galaxies are reported inthe mid-infrared from 8 - 18 microns using the Keck Telescopes with spatialresolution approaching the diffraction limit. All of the galaxies observed showevidence of strong interactions based on optical morphologies. For thesegalaxies, a substantial fraction, usually more than 50%, of the infraredluminosity is generated in regions ranging in sizes from 100pc -- 1 Kpc.Nuclear starbursts often dominate the infrared luminosity, but this is notalways true. In some galaxies, most notably NGC 6090, substantial infraredluminosity greatly in excess of the nuclear luminosity is generated in regionsassociated with the physical interaction between two galaxies. The radioemission is a good tracer of the location of high luminosity young stars. Thevisual/ultraviolet radiation output of the nearby star forming galaxies isdominated by emission from regions that are generally not producing the copiousinfrared luminosity of the systems. The regions of high infrared luminosity inlocal starburst galaxies are significantly smaller than the galaxies as awhole. The integrated spectral energy distributions (SEDs) of these galaxiesare very different from the SEDs of the regions of star formation. If the SEDsof star-forming regions in these galaxies reflect the SEDs found in forminggalaxies at high redshift, the distant galaxies should be dominated by the midand far-infrared luminosity output far more than the integrated luminous outputof nearby starburst galaxies would suggest.Comment: 33pages, 4 tables, 8 figures, Accepted for publication in Astronomical Journa