Kinematic evidence of minor mergers in normal Sa galaxies: NGC 3626, NGC 3900, NGC 4772, and NGC 5854

BVRI and H alpha imaging and long-slit optical spectroscopic data are prese nted for four morphologically normal and relatively isolated Sa galaxies, N GC 3626, NGC 3900, NGC 4772, and NGC 5854. VLA H I synthesis imaging is pre sented for the first three objects. In all four galaxies, evidence of kinem atic decoupling of ionized gas components is found in the long-slit spectro scopic data; the degree and circumstances of the distinct kinematics vary f rom complete counterrotation of all of the gas from all of the stars (NGC 3 626) to nuclear gas disks decoupled from the stars (NGC 5854) to anomalous velocity central gas components (NGC 3900 and NGC 4772). In the three objec ts mapped in H I, the neutral gas extends far beyond the optical radius, R- HI/R-25 greater than or equal to 2. In general, the I-I I surface density i s very low, and the outer H I is patchy and asymmetric (NGC 3900) or found in a distinct ring, exterior to the optical edge (NGC 3626 and NGC 4772). W hile the overall H I velocity fields are dominated by circular motions, str ong warps are suggested in the outer regions by bending of the minor axis i sovelocity contours (NGC 3900) and/or systematic shifts in position angle b etween inner and outer rings (NGC 3626 and NGC 4772). In the interior, coin cidence is found between the H alpha and H r in rings, sometimes partial an d crisscrossed by dust lanes. Optical imaging is also presented for NGC 413 8 previously reported by Jore et al. to show counterrotating stellar compon ents. The multiwavelength evidence is interpreted in terms of the kinematic "memory" of past minor mergers in objects that otherwise exhibit no morpho logical signs of interaction.