2MASS/SDSS CLOSE MAJOR-MERGER GALAXY PAIRS

Abstract

We select a close "major-merger candidate" galaxy pair sample in order to calculate the K_s 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, K_s -band magnitude difference ΔK_s ≤ 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 deg^2. 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 10^9 to 10^(11.5) 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 10^(11) M_☉ . The derived LF combined with merger model timescales give local merger rates per unit volume which decrease with masses greater than 10^(11) M_☉ .
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