Statistical Properties of the Emission in Mixed-Morphology (E + S) Pairs. II. MIR/FIR Results

摘要

We present a statistical analysis of mid/far-IR emission properties for a mixed morphology (E/S0 + S/I) sample of galaxy pairs based on a new co-addition of the IRAS database. The sample is large and diverse enough (~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 μm 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 correlation between the IR luminosity and interaction class, (2) a poor anticorrelation between IR luminosity and projected separation in pairs where 25 μm seems to be more sensitive than FIR, (3) an increase in the ratio of present to past star formation (IR luminosities scaled to LB luminosity) from early to late type spiral pair components, and (4) a high-mass (M ≥ 10 M⊙) star formation rate (SFR) higher in paired Sc spirals than that in isolated Sc galaxies by a factor ~2–3.