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Paper: Frequency and Impact of Galaxy Mergers and Interactions over the Last 7 Gyr
Volume: 396, Formation and Evolution of Galaxy Disks
Page: 337
Authors: Jogee, S.; Miller, S.; Penner, K.; Bell, E.F.; Conselice, C.; Skelton, R.E.; Somerville, R.S.; Rix, H-W.; Barazza, F.D.; Barden, M.; Borch, A.; Beckwith, S.V.; Caldwell, J.A.R.; Häußler, B.; Heymans, C.; Jahnke, K.; McIntosh, D.; Meisenheimer, K.; Papovich, C.; Peng, C.Y.; Robaina, A.; Sanchez, S.; Wisotzki, L.; Wolf, C.
Abstract: We explore the history and impact of galaxy mergers and interactions over z ∼ 0.24 − 0.80, based on HST ACS, Combo-17, and Spitzer 24 μm data of ∼ 4500 galaxies in the GEMS survey. Using visual and quantitative parameters, we identify galaxies with strong distortions indicative of recent strong interactions and mergers versus normal galaxies (E/S0, Sa, Sb- Sc, Sd/Irr). Our preliminary results are: (1) The observed fraction F of strongly disturbed systems among high mass (M ≥ 2.5 × 1010 M) galaxies is ∼ 9% to 12% in every Gyr bin over z ∼ 0.24 − 0.80. The corresponding merger rate is ∼ a few ×10−4 galaxies Gyr−1 Mpc−3. The fraction F shows fair agreement with the merger fraction of mass ratio ≥ 1:10 predicted by several ΛCDM-based simulations. (2) For M ≥ 1.0×109 M systems, the average star formation rate (SFR) of strongly disturbed systems is only modestly enhanced with respect to normal galaxies. In fact, over z ∼ 0.24 − 0.8, strongly disturbed systems only account for a small fraction (< 30%) of the total SFR density. This suggest that the behavior of the cosmic SFR density over z ∼ 0.24 − 0.80 is predominantly shaped by normal galaxies.
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