The Cone - like H Α Nebula in Ngc 4945 : a Galactic Superwind Bow Shock ?

Received ; accepted – 2 – ABSTRACT We find that a non-axisymmetric bow shock model, with an appropriate choice of parameters, could fit the line splitting velocity field of the cone-like Hα nebula in NGC 4945 better than a canonical cone model. Meanwhile, the bow shock model could also reproduce the morphology of the Hα nebula. The bow shock results from the interaction of the galactic superwinds with a giant HII region. It is implied that the starburst ring or disk around the galactic nucleus should be generating strong winds, and the bright Hα knot northwest of the nucleus be suffering an anisotropic mass loss process.