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Abstract
Galactic interactions are a significant force in the evolution and transformation of galaxies, often producing large infrared luminosities and regions of intense star formation. The present study was initiated to determine the structure of a diverse sample of interacting systems, and to investigate the nature and extent of induced galactic activity. The objects in this study include the unusual ring galaxy Arp 148 (Mayall's Object); two long-tailed galaxies, NGC 2623 and NGC 4038/39 (the 'Antennae'); a colliding spiral/elliptical system, NGC 1143/44; a blue compact galaxy, II Zw 40; the prototypical starburst galaxy, M82; and the luminous merging galaxy, Arp 220. Infrared measurements have proven to be very useful (and often essential) for studies of highly obscured, luminous galaxies; in the present investigation, near- and far-infrared continuum measurements are utilized in several lines of inquiry: (i) To obtain multicolor 1-3 (mu)m galaxy scans for this study, a simultaneous 3-color near-infrared photometer was designed, constructed, and implemented at McDonald Observatory. In parallel with this instrumental effort, near-infrared galaxy measurements were obtained using the Infrared Telescope Facility on Mauna Kea, and the capability to obtain and analyze high resolution far-infrared scans was developed utilizing the Kuiper Airborne Observatory. (ii) Near-infrared and/or optical surface photometry was obtained for the program galaxies to determine the structure of the tidally-distorted population of evolved stars; where possible, the dynamical history of the interaction is inferred from the stellar morphology. (iii) A multicolor decomposition method was developed to objectively interpret the unusual near-infrared colors observed in NGC 2623, Arp 148, NGC 1143/44, II Zw 40, NGC 4038/39, and M82. (iv) New observational and analytical techniques were used to obtain high-resolution profiles of the luminous peculiar galaxies M82 and Arp 220 in the far-infrared spectral region, where virtually all of their energy is radiated; important structural information is inferred on angular scales substantially smaller than the conventional diffraction limit.