High Resolution IRAS Observations of Interacting Systems in the IRAS Bright Galaxy Sample

March 1993 • 1993AJ....105..864S

Authors • Surace, Jason A. • Mazzarella, Joseph • Soifer, B. T. • Wehrle, Ann E.

Abstract • A sample of morphologically selected interacting galaxies has been chosen from the 60 micron flux density limited IRAS Bright Galaxy Sample [Soifer et al., ApJ, 320,238(1987)]. Using the HIRES algorithm [Aumann et al., AJ, 99, 1674(1990)] and one-dimensional coaddition, the IRAS survey data for these galaxies were analyzed and the infrared fluxes at 12, 25, 60, and 100 microns for the resolved components have been determined where possible. Of the 56 potentially resolvable interacting groups, 22 systems have been resolved yielding fluxes for a total of 51 galaxies. In about 2/3 of the resolved pairs, both galaxies are bright in the infrared. A set of isolated noninteracting galaxies with a similar distribution of blue luminosities was chosen from the IRAS Bright Galaxy Sample for comparison with the interacting galaxies. For the current sample of interacting systems resolved by IRAS the primary conclusions are as follows: (a) It is not possible to distinguish individual interacting galaxies from isolated galaxies of similar blue luminosity on the basis of infrared properties alone. Interactions of the type sampled here do not, therefore, produce any unique IR signatures in individual galaxies. The relatively large intrinsic dispersion of normal galaxy properties is likely responsible for this fact. (b) No direct correlation was found between measures of interaction strength and indicators of enhanced star formation within the resolved systems. (c) Comparison of the interacting and isolated samples indicates substantial differences between their distributions of far-infrared color ratios, luminosities, and surface brightnesses. These differences can be attributed to the expected heating of the gas rich interstellar medium due to the triggering of starbursts in the interacting galaxies. Even during the early stages of interaction spanned by these systems, tidal perturbations appear to substantially boost far-infrared indicators of star formation compared to noninteracting systems.

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