Cen a and Its Interaction with the X-ray Emitting Interstellar Medium

As the closest radio galaxy, Centaurus A is a powerful laboratory for the X-ray study of radio-emitting structures and their interactions with the hot interstellar medium (ISM). This paper details our interpretation of the remarkable X-ray enhancement which caps the inner southwest radio lobe, at a radius of about 6 kpc from the galaxy center. The shell of X-rayemitting gas is hotter than the ambient ISM, and overpressured by a factor of 100. We argue that it is heated compressed material behind the supersonicallyadvancing bow shock of the radio lobe, the first example of the phenomenon to be clearly detected. The results demonstrate that Cen A is actively re-heating nearby X-ray-emitting gas. The shell’s kinetic energy is 5 times its thermal energy, and exceeds the thermal energy of the ISM within 15 kpc of the center of the galaxy. As the shell dissipates it will have a major effect on Cen A’s ISM, providing distributed heating.