2005ApJ...624L..77O

Chandra observations of NGC 4636 show disturbances in the galaxy X-ray halo, including armlike high surface brightness features (tentatively identified as active galactic nucleus-driven shocks) and a possible cavity on the west side of the galaxy core. We present Chandra and XMM-Newton spectral maps of NGC 4636 that confirm the presence of the cavity and show it to be bounded by the arm features. The maps also reveal a ∼15 kpc wide plume of low-temperature, high-abundance gas extending 25-30 kpc to the southwest of the galaxy. The cavity appears to be embedded in this plume, and we interpret the structure as being entrained gas drawn out of the galaxy core during previous episodes of active galactic nucleus (AGN) activity. The end of the plume is marked by a well-defined edge, with significant falls in surface brightness, temperature, and abundance, indicating a boundary between galaxy and group/cluster gas. This may be evidence that as well as preventing gas cooling through direct heating, AGN outbursts can produce significant gas mixing, disturbing the temperature structure of the halo and transporting metals out from the galaxy into the surrounding intragroup medium.