A radio study of neutral gas and dust in the radio galaxy 3C 293

Abstract

We have observed broad H I absorption in the radio galaxy 3C 293 using Multi-Element Radio Linked Interferometric Network (MERLIN) at 0.2-arcsec angular resolution and the Giant Meterwavelength Radio Telescope (GMRT) at arcsec resolution.Extensive H I is found in absorption across the centre of this peculiar radio galaxy, allowing a detailed study of the dynamics of the neutral gas on linear scales down to , 160 pc.In optical depth positionvelocity diagrams across the central few kpc we detect a distinct velocity gradient of 179 km s 21 arcsec 21 associated with the broad absorption.This is interpreted as a ring of neutral gas rotating around the suspected position of the active galactic nucleus (AGN).The radius of this high velocity gradient ring is found to be .0.74 arcsec (600 pc), implying an upper limit upon the enclosed mass of 3:9 10 9 sin 22 i M ( , assuming a near edge-on disc with an inclination of i.The optical depth of H I is mapped across the entire central region of 3C 293 showing enhancements of a factor of 4 in the areas that are co-spatial with dust lanes seen in Hubble Space Telescope (HST) imaging of this galaxy.