Galaxy evolution in merging clusters: The passive core of the "Train Wreck" cluster of galaxies, A520

Understand

The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang.

• With the increased availability of multi-object spectroscopy and X-ray data an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales.
• Our goal is to probe how these mergers affect the evolution and content of their member galaxies.
• We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short lived) burst of star formation? We obtained optical spectroscopy of >400 galaxies in the field of the merging cluster Abell 520.