Interacting Galaxies In The A901/902 Supercluster With Stages

We present a study of galaxy mergers and the influence of environment in the Abell 901/902 supercluster at z similar to 0.165, based on 893 bright (R-Vega = 10(9) M-circle dot) galaxies. We use HST ACS F606W data from the Space Telescope A901/902 Galaxy Evolution Survey, COMBO-17, Spitzer 24 mu m, and XMM-Newton X-ray data. Our analysis utilizes both a physically driven visual classification system and quantitative CAS parameters to identify systems which show evidence of a recent or ongoing merger of mass ratio >1/10 (i.e., major and minor mergers). Our results are (1) after visual classification and minimizing the contamination from false projection pairs, we find that the merger fraction f(merge) is 0.023 +/- 0.007. The estimated fractions of likely major mergers, likely minor mergers, and ambiguous cases are 0.01 +/- 0.004, 0.006 +/- 0.003, and 0.007 +/- 0.003, respectively. (2) All the mergers lie outside the cluster core of radius R < 0.25 Mpc: the lack of mergers in the core is likely due to the large galaxy velocity dispersion in the core. The mergers, instead, populate the region (0.25 Mpc < R