Termination Shocks and the Extended X-Ray Emission in Mrk 78

Abstract

Subarcsecond imaging of the X-ray emission in the type 2 active galactic nucleus (AGN) Mrk 78 with Chandra shows complex structure with spectral variations on scales from ~200 pc to ~2 kpc. Overall the X-ray emission is aligned E-W with the radio (3.6 cm) and narrow emission line region as mapped in [O III], with a marked E-W asymmetry. The eastern X-ray emission is mostly in a compact knot coincident with the location where the radio source is deflected, while the western X-ray emission forms a loop or shell ~2 kpc from the nucleus with radius ~0.7 kpc. There is suggestive evidence of shocks in both the eastern knot and the western arc. Both these positions coincide with large changes in the velocities of the [O III] outflow. We discuss possible reasons why the X-ray shocks on the western side occur ~1 kpc farther out than on the eastern side. We estimate that the thermal energy injected by the shocks into the interstellar medium corresponds to 0.05%-0.6% of the AGN bolometric luminosity.