Optical IFU observations of the brightest cluster galaxy NGC 4696: The case for a minor merger and shock-excited filaments

We present deep optical integral-field spectroscopic observations of the nearby (z ∼ 0.01) brightest cluster galaxy NGC 4696 in the core of the Centaurus Cluster, made with the Wide Field Spectrograph on the Australian National University 2.3 m telescope at Siding Spring Observatory. We investigate the morphology, kinematics, and excitation of the emission-line filaments and discuss these in the context of a model of a minor merger. We suggest that the emission-line filaments in this object have their origin in the accretion of a gas-rich galaxy and that they are excited by v ∼ 100-200 km s^-1 shocks driven into the cool filament gas by the ram pressure of the transonic passage of the merging system through the hot halo gas of NGC 4696.