The Deep2 Galaxy Redshift Survey: Evolution of Close Galaxy Pairs and Major-Merger Rates Up to z ~ 1.2

Abstract

We derive the close, kinematic pair fraction and merger rate up to z ~ 1.2 from the initial data of the DEEP2 Redshift Survey. Assuming a mild luminosity evolution, the number of companions per luminous galaxy is found to evolve as (1+z)^{m}, with m = 0.51+-0.28; assuming no evolution, m = 1.60+-0.29. Our results imply that only 9% of present-day $L^{*}$ galaxies have undergone major mergers since z ~ 1.2 and that the average major merger rate is about 4* 10^{-4} h^{3} Mpc^{-3} Gyr^{-1} for z ~ 0.5 - 1.2. Most previous studies have yielded higher values.