Evidence for an outflow from the Seyfert galaxy NGC

Abstract

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\\arcsec\\ from the core, show the øiii\\ emission line to consist of two velocity components, both blue-shifted from the systemic radial velocity, with velocity widths of 140\\kms\\ and separated by 120\\kms. This region is co-spatial with weak extended radio emission and is suggestive of a centrally driven outflow. The øiii\\ line spectrum and image of this region have been modelled as an outflowing conical structure at 50\\degr\\ to the line of sight with a half opening angle of 23\\degr . In addition to the extended structure, high resolution MERLIN observations of the 18-cm nuclear radio emission reveal a compact (1\\arcsec) radio triple source in PA 73$^{\\circ}$. 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.