Optical IFU Observations of the Brightest Cluster Galaxy NGC 4696: The Case for a Minor Merger and Shock-excited Filaments

TL;DR

This study uses optical integral-field spectroscopy to analyze the emission-line filaments in NGC 4696, proposing they originate from a minor merger and are shock-excited by ram pressure during the galaxy's interaction.

Contribution

It provides new evidence linking filament excitation to shocks caused by a minor merger in the brightest cluster galaxy NGC 4696.

Findings

Filaments likely result from accretion of a gas-rich galaxy.

Filament excitation is driven by shocks at 100-200 km/s.

Minor merger scenario explains filament morphology and kinematics.

Abstract

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 (WiFeS) on the ANU 2.3m 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 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.