The Leo I Cloud: Secular Nuclear Evolution of NGC 3379, NGC 3384, and NGC 3368?

Abstract

The central regions of the three brightest members of the Leo I galaxy group - NGC 3368, NGC 3379, and NGC 3384 - are investigated by means of two-dimensional spectroscopy. In all three galaxies we have found separate circumnuclear stellar and gaseous subsystems - more probably, disks - whose spatial orientations and spins are connected to the spatial orientation of the supergiant intergalactic H I ring reported previously by Schneider et al. and Schneider. In NGC 3368 the global gaseous disk seems also to be inclined to the symmetry plane of the stellar body, being probably of external origin. Although the rather young mean stellar age and spatial orientations of the circumnuclear disks in NGC 3379, NGC 3384, and NGC 3368 could imply their recent formation from material of the intergalactic H I cloud, the timescale of these secondary formation events, on the order of 3 Gyr, does not support the collision scenario of Rood & Williams but is rather in line with the ideas of Schneider regarding tidal interactions of the galaxies with the H I cloud on timescales of the intergroup orbital motions.