A neutral hydrogen study of the Seyfert galaxy NGC 5033

Neutral hydrogen observations of 22.7 × 18.5 arcsec² resolution are presented for the Seyfert type 1 galaxy NGC 5033. Our measurements show that the total Hi mass of the galaxy is 7.0 × 10⁹ M_⊙ and that it is receding at 870 km s^-1. The column density map features prominent Hi spiral arms and an asymmetric plume of Hi which extends ∼6 kpc south of the galaxy. We find a well-ordered velocity field and the large-scale kinematical warp in the galactic disc has been modelled. The inner region of the velocity field is well fitted by a flat, inclined disc with inclination 68° and position angle 352°, but due to warping these fall to 64° and 342°, respectively, at large radii. Attention is paid to factors that may be related to Seyfert activity in the nucleus and we find some evidence for a previous tidal encounter but little evidence for a bar, or significant non-circular motions in the central regions. Large concentrations of H I at the galactic centre appear to show no evidence of interaction with the active nucleus.