The optical jet of the galaxy NGC 4258 - Interaction with the interstellar medium

Monochromatic Hα and red continuum images, as well as high-resolution aperture synthesis ^12^CO maps, were obtained in order to study the optical jet of the spiral galaxy NGC 4258. The jet morphology shows strong interaction with the ambient interstellar medium. The optical emission of the jet is due to line emission arising possibly from gas of the ambient interstellar medium which has been entrained and shocked by the radio-emitting gas. The jet near the center is resolved and has a width of ~ 200 pc. The CO observations show two clouds on each side of the nucleus; these clouds outline a channel, and the Hα jet falls right into this channel. These observations are consistent with the jet being in or making a small angle with the galaxy plane. It is suggested that the channel represents a tunnel bored by energetic material and that jet activity in NGC 4258 has been intermittent in the recent past. The interstellar medium may play an important role in making jets detectable optically and in shaping their forms.