Key points are not available for this paper at this time.
We present Spitzer observations for a sample of close major-merger galaxy pairs (KPAIR sample) selected from 2MASS/SDSS-DR3 cross-matches. The goals are to study the star formation activity in these galaxies and to set a local bench mark for the cosmic evolution of close major mergers. The Spitzer KPAIR sample (27 pairs, 54 galaxies) includes all spectroscopically confirmed S+S and S+E pairs in a parent sample that is complete for primaries brighter than K=12. 5 mag, projected separations of 5< s < 20 kpc/h, and mass ratios<2. 5. The Spitzer data consist of images in 7 bands (3. 6, 4. 5, 5. 8, 8, 24, 70, 160 um). Compared to single spiral galaxies in a control sample, only spiral galaxies in S+S pairs show significantly enhanced specific star formation rate (sSFR=SFR/M), whereas spiral galaxies in S+E pairs do not. Furthermore, the SFR enhancement of spiral galaxies in S+S pairs is highly mass-dependent. Only those with M 10^10. 5 M_ show significant enhancement. Relatively low mass (M 10^10 M_) spirals in S+S pairs have about the same SFR/M compared to their counterparts in the control sample. There is evidence for a correlation between the global star formation activities (but not the nuclear activities) of the component galaxies in massive S+S major-merger pairs (the "Holmberg effect"). There is no significant difference in the SFR/M between the primaries and the secondaries, nor between spirals of SEP<1 and those of SEP. 1. The contribution of KPAIR galaxies to the cosmic SFR density in the local universe is only 1. 7%.
Xu et al. (Mon,) studied this question.