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| Paper: |
The Redshift Evolution of Wet, Dry, and Mixed Galaxy Mergers from Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey |
| Volume: |
399, Panoramic Views of Galaxy Formation and Evolution |
| Page: |
298 |
| Authors: |
Lin, L.; Patton, D.R.; Koo, D.C.; Casteels, K.; Hsieh, B.C.; the DEEP2 team |
| Abstract: |
We carry out a study of the redshift evolution of the galaxy pair fractions and merger rates for different types of galaxies using kinematic pairs selected from the DEEP2 Redshift Survey, combined with other surveys at lower Redshifts. Parameterizing the evolution of the pair fraction as (1 + z)m, we find that the companion rate increases mildly with increasing redshift with m = 0.41 ± 0.20 for L* galaxies. Blue galaxies show slightly faster evolution in the blue companion rate with m = 1.27±0.35 while red galaxies have had fewer red companions in the past as evidenced by the negative slope m = −0.92 ± 0.59. With further assumptions on the merger time scale and the fraction of pairs that will merge, the galaxy major merger rates are estimated to be ∼ 10−3h3Mpc−3Gyr−1 for 0.1 < z < 1.2, dominated by wet mergers (gas-rich mergers) until very recently. However, the fraction of dry (gas-poor mergers) and mixed mergers out of the total merger events increase over time, from 8% and 24% at z ∼ 1 to 25% and 44% at z = 0 respectively. Our results also suggest that the three types of mergers lead to the formation of red galaxies in different mass regimes: the wet mergers and/or mixed mergers may be partially responsible for producing red galaxies with intermediate masses while a significant portion of massive red galaxies is assembled through dry mergers at later times. |
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