THE DEEP2 GALAXY REDSHIFT SURVEY: EVOLUTION OF CLOSE GALAXY PAIRS AND MAJOR-MERGER RATES UPTO z ～ 1.2

摘要

We derive the close, kinematic pair fraction and merger rate up to redshift 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 x 10~(-4) h~3 Mpc~(-3) Gyr~(-1) for z ～ 0.5-1.2. Most previous studies have yielded higher values.