The bulge-disk orthogonal decoupling in galaxies: NGC 4698

The R-band isophotal map of the Sa galaxy NGC 4698 shows that the inner region of the bulge structure is elongated perpendicularly to the major axis of the disk; this is also true for the outer parts of the bulge if a parametric photometric decomposition is adopted. At the same time, the stellar component is characterized by an inner velocity gradient and a central zero-velocity plateau along the minor and major axes of the disk, respectively. This remarkable geometric and kinematic decoupling suggests that a second event occurred in the formation history of this galaxy.