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arXiv · 1002.3648

Local Benchmarks for the Evolution of Major-Merger Galaxies -- Spitzer Observations of a K-Band Selected Sample

C. Kevin Xu·Donovan Domingue·Yi-Wen Cheng·Nanyao Lu·Jiasheng Huang·Yu Gao·Joseph M. Mazzarella·Roc Cutri·Wei-Hsin Sun·Jason Surace
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Abstract

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 $\rm M \gsim 10^{10.5} M_\sun$ show significant enhancement. Relatively low mass ($\rm M \sim 10^{10} M_\sun$) 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%.

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C. Kevin Xu, Donovan Domingue, Yi-Wen Cheng, Nanyao Lu, Jiasheng Huang, Yu Gao, Joseph M. Mazzarella, Roc Cutri, Wei-Hsin Sun, Jason Surace. 2010-02-18. Local Benchmarks for the Evolution of Major-Merger Galaxies -- Spitzer Observations of a K-Band Selected Sample. https://doi.org/10.1088/0004-637x%2F713%2F1%2F330

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