We present adaptive optics assisted OASIS Â integral field spectrography of the S0 galaxy NGCÂ 4621 .
Two-dimensional stellar kinematical maps ( mean velocity and dispersion ) reveal the presence of a \sim 60 Â pc diameter counter-rotating core ( CRC ) , the smallest observed to date .
The OASIS Â data also suggests that the kinematic center of the CRC is slightly offset from the center of the outer isophotes .
This seems to be confirmed by archival HST/ STIS Â data .
We also present the HST/WFPC2 V - I colour map , which exhibits a central elongated red structure , also slightly off-centered in the same direction as the kinematic centre .
We then construct an axisymmetric model of NGC 4621 : the two-integral distribution function is derived using the Multi-Gaussian Expansion and the Hunter & Qian ( [ 1993 ] ) formalisms .
Although the stellar velocities are reasonably fitted , including the region of the counter-rotating core , significant discrepancies between the model and the observations demonstrate the need for a more general model ( e.g . a three-integral model ) .