Emission from hot, ionised gas distinguishes active galactic nuclei (AGNs) from quiescent galaxies. However, conventional models for AGNs depend on the distribution and kinematics of colder, neutral media. Firstly, the host galaxy is a massive reservoir of neutral gas which might ultimately feed an energetic accretion disc, although the means by which gas funnels down to sub-parsec scales in not well understood (Rees 1984). Secondly, the unifying schemes for AGNs propose that the apparent differences between broad-line AGNs (i.e. Seyfert 1s) and narrow-line AGNs (Seyfert 2s) result from selective obscuration through neutral, dusty gas located along the sight-line to the broad-line region (Antonucci & Miller 1985).
Exploring the neutral gas in AGNs is challenging because the surface brightness of emission is generally too faint to detect on scales much smaller than . We are instead continuing a programme to explore neutral hydrogen (H I) in absorption towards AGNs with the goal of establishing the distribution and kinematics on scales as small as , or roughly 10 parsecs in the nearest Seyfert galaxies (Pedlar et al. 1995; Mundell et al. 1995; Gallimore et al. 1994). In this work, we present MERLIN observations of 21 cm absorption towards the Seyfert 1.5 nucleus of Mkn 6. The localisation of the H I absorption suggests a particular alignment between the host galaxy disc and the radio jet. After first describing the observations and results, we discuss the implications of this alignment in further detail. For comparison with earlier papers, we adopt a distance of 77 Mpc to Mkn 6, appropriate for km s-1 Mpc-1, and giving a scale of 1" = 374 pc (Meaburn et al. 1989).
© European Southern Observatory (ESO) 1998
Online publication: April 15, 1998