2000A&A...357....7P

We report parsec-scale resolution observations of neutral hydrogen seen in absorption in the λ=21cm line in the H₂O megamaser galaxy 793. We find that the total HI column density of 5x10²²((T_sp)/(100K))cm^–2 is divided into three narrow (FWHM≤16km/s) and one broad component (FWHM50km/s). The narrow components have HI column densities of ∼5x10²¹((T_sp)/(100K))cm^–2 and there is evidence that they have sizes ≃15pc and HI densities of ∼150((T_sp)/(100K))cm^–3. The broad absorption component shows a velocity gradient in the same direction as the CO disk observed in this source. We argue that this broad component could be due to a circumnuclear disk or torus. The observed velocity gradient implies that this structure has radius ∼50-100pc.