introduction

Clusters of galaxies are complex dynamical structures and their cores are subject to an array of interesting physical processes. Constraints from imaging X-ray observations suggest that the hot X-ray emitting intracluster medium (ICM) in the core regions of rich clusters is radiatively cooling on timescales shorter than the life of the cluster, giving rise to cooling flows (Fabian, 1994, and references therein). The central dominant galaxy present in many clusters often hosts a radio loud active galactic nucleus (AGN). It has been suggested (e.g., Binney & Tabor, 1995) that cooling flows and central cluster radio galaxies are intimately related via complex feedback processes. It is easy to see how radio galaxy activity resulting from black hole accretion can be associated with a cooling flow. However, the impact of a radio galaxy on its environment is much less clear.

Theoretically, we expect radio jets to inflate cocoons of relativistic plasma that expand into the surrounding ICM (e.g. Reynolds et al., 2001b; Begelman & Cioffi, 1989; Kaiser & Alexander, 1997, , hereafter RHB). The energy input by this process has recently come under investigation for its potential role in heating cluster cores (Reynolds et al., 2001a; Quilis et al., 2001; Brüggen et al., 2001). However, while our simulations suggest that about half of the energy injected by the jets can be thermalized in the cluster center, numerical simulations of this process still carry a large degree of uncertainty, since limited computational resources require significant simplications. In order to verify the validity of the assumptions and to design future models, we require guidance from observations of radio-galaxy/cluster interactions.

Imaging X-ray observatories, such as the Chandra X-ray Observatory (CXO), provide a direct probe of this interaction. Both ROSAT and CXO observations of Perseus A have found X-ray cavities coincident with the radio lobes (Fabian et al., 2000; Boehringer et al., 1993), surrounded by X-ray shells which appear to be slightly cooler than the unperturbed ICM (see, for example, RHB for a possible explanation). Similar features are seen in CXO observations of Hydra A (David et al., 2001; McNamara et al., 2000) and Abell 2052 (Blanton et al., 2001).

In this Letter, we present CXO observations of the rich galaxy cluster Abell 4059 ($z=0.049$). The cD galaxy of A4059 hosts the FR-I radio galaxy PKS 2354-35. A short ROSAT High Resolution Imager (HRI) observation of this source suggested the presence of two ICM cavities at the same position angle as the radio lobes (Huang & Sarazin, 1998, , hereafter HS). In § 2 we discuss our observations, confirming the presence of these cavities, and show that A4059 displays significant additional morphological complexity. Constraints on models for this source are discussed in § 3, § 4 presents our conclusions. We assume a Hubble constant of $H_0=65 \hbox{$\hbox{${\rm\thinspace km}{\rm\thinspace s}^{-1}\,$}{\rm\thinspace Mpc}^{-1}$}$ and $q_0 = 1/2$, giving a linear scale of $1\, {\rm kpc\,arcsec^{-1}} = 0.492\, {\rm kpc\,pixel^{-1}}$.