Interacting galaxies in the A901/902 supercluster with stages

Abstract

We present a study of galaxy mergers and the influence of environment in the Abell 901/902 supercluster at z ∼ 0.165, based on 893 bright (R Vega≤ 24) intermediate-mass (M * ≥ 10 9 M) galaxies. We use HST ACS F606W data from the Space Telescope A901/902 Galaxy Evolution Survey, COMBO-17, Spitzer 24 μm, 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