2MASS/SDSS close major-merger galaxy pairs

Abstract

We select a close "major-merger candidate" galaxy pair sample in order to calculate the Ks luminosity function (LF) and pair fraction representative of the merger/interaction component of galaxy evolution in the local universe. The pair sample (projected separation 5 h-1 kpc ≤ r ≤ 20 h-1 kpc, Ks-band magnitude difference ΔKs ≤ 1 mag) is selected by combining the Two Micron All Sky Survey (2MASS) with the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). The resulting data set contains 340 galaxies covering 5800 deg2. A stellar mass function is also translated from the LF. A differential pair fraction displays nearly constant fraction of galaxy pairs as a function of galaxy mass from 109 to 1011.5 M⊙. The differential pair fraction is less subject to absolute magnitude bias due to survey limitations than the standard total pair fraction. These results suggest that major-merger candidate pairs in the 0< z <0.1 universe are developed from ∼1.6% of the galaxy population without dependence on galaxy mass for pair components below 1011 M⊙. The derived LF combined with merger model timescales give local merger rates per unit volume which decrease with masses greater than 1011 M⊙.