The extended Hα-emitting filaments surrounding NGC 4696, the central galaxy of the Centaurus cluster

Abstract

We present images of NGC 4696, the central galaxy in the Centaurus cluster, showing the large extent of cool filaments that are bright in Ha line emission. These filaments share the detailed structure of both the central dust lane and the inner regions of the arc-like plumes seen in soft X-ray emission. The X-ray gas is at its coolest and most absorbed in this same region. The smoothness of the features implies that the local environment is not strongly turbulent. We suggest that these filaments are shaped either by confinement due to a strong magnetic field, or by bulk flows within the intracluster medium. We propose that, like similar filamentary systems in the core of clusters, these cooler components have been drawn out of the central galaxy behind buoyant gas bubbles from previous episodes of radio activity. We find a spur of low-frequency radio emission leading to a region of low X-ray pressure within the intracluster medium, supporting this interpretation. © 2005 RAS.