Major mergers on massive early-type galaxies in clusters

Sukyoung Yi (Yonsei University)

Major mergers provide an important channel for morphology transformation. In the hierarchical merger paradigm, major mergers are supposed to be rare at low redshifts and in massive clusters. The recent observational study of Sheen et al. (2012) however found a large fraction (~40%) of massive early-type galaxies in massive clusters at z=0.1 showing morphological signs of major mergers, which is in contrast to the theoretical expectation. We present a theoretical explanation to this apparent controversy. We use cosmological volume simulation to trace dark matter clusterings and semi-analytic modeling technique to trace galaxy formation. We also investigate on the lifetime of major merger features using hydrodynamic simulations. The conclusion is that we can reproduce the fraction of galaxies with merger features. They are not likely the merger remnants in situ in the current cluster but merger relics from previous, smaller halo environments whe re mergers were easier. The work was published in A&A (Yi et al. 2013) and covered in Science (Editor's choice section).

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