Cen A and its interaction with the x-ray emitting interstellar medium

Abstract

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-ray-emitting gas is hotter than the ambient ISM, and overpressured by a factor of 100. We argue that it is heated compressed material behind the supersonically-advancing 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 $\sim 5$ 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.