Statistical properties of the emission in mixed-morphology (E+S) pairs. II. MIR/FIR results

We present a statistical analysis of mid/far-IR emission properties for a m ixed morphology (E/S0+S/I) sample of galaxy pairs based on a new co-additio n of the IRAS database. The sample is large and diverse enough (similar to 130 pairs) to permit discrimination of pairs by component morphologies and interaction classes. It samples a large enough volume of space to enable a nonparametric estimate of the far-infrared luminosity function (FIRLF). We find average factors of 3 and 5 enhancement in FIR and 25 mum luminosities, respectively, for the late-type components relative to an isolated galaxy control sample. This is interpreted as the MIR/FIR signature of interaction induced star formation. A more detailed study reveals (1) a strong correla tion between the IR luminosity and interaction class, (2) a poor anticorrel ation between IR luminosity and projected separation in pairs where 25 km s eems to be more sensitive than FIR, (3) an increase in the ratio of present to past star formation (IR luminosities scaled to L-B luminosity) from ear ly to late type spiral pair components, and (4) a high-mass (M greater than or equal to 10 M.) star formation rate (SFR) higher in paired Sc spirals t han that in isolated Sc galaxies by a factor similar to2-3.