Evidence for an outflow from the Seyfert galaxy NGC

New observations using narrow band imaging, long-slit spectroscopy and MERLIN observations of the nuclear region of the Seyfert galaxy NGC 4051 have been made. An edge brightened, triangular region of ionized gas extending 420 pc from the centre of the galaxy has been detected. Long-slit spectra of this ionised gas, taken at 1.5 ′′ from the core, show the [O iii] 5007-u emission line to consist of two velocity components, both blue-shifted from the systemic radial velocity, with velocity widths of 140 kms −1 and separated by 120 kms −1 . This region is co-spatial with weak extended radio emission and is suggestive of a centrally driven outflow. The [O iii] 5007-u line spectrum and image of this region have been modelled as an outflowing conical structure at 50 ◦ to the line of sight with a half opening angle of 23 ◦ . In addition to the extended structure, high resolution MERLIN observations of the 18-cm nuclear radio emission reveal a compact (1 ′′ ) radio triple source in PA 73 ◦ . This source is coincident with the HST-imaged emission line structure. These high resolution observations are consistent with a more compact origin of activity (i.e. a Seyfert nucleus) than a starburst region.