IAU Symposium Abstract S186-045P


Nuclear Stellar Counterrotation in Early-Type Disk Galaxies: NGC 4698 and IC 4889


J.C. Vega Beltr'an1, F. Bertola2, E.M. Corsini2,
and A. Pizzella2
1 Telescopio Nazionale Galileo, Osservatorio di Padova, Italy < jvega@astrpd.pd.astro.it >
2 Dipartimento di Astronomia, Universit\`a di Padova, Italy < bertola,corsini,pizzella@astrpd.pd.astro.it >



We report the case of the presence of a fraction of stars counterrotating with respect to the main stellar body in the nuclear regions of two early-type disk galaxies. They are the Sa NGC 4698 and the S01/2(5) IC 4889. The major axis stellar kinematics reveals an observed zero velocity gradient in the central +/- 6'' (about +/- 0.6 kpc) of NGC 4698 and in +/- 2" (about +/- 0.5 kpc) of IC 4889. Outside their stellar rotation velocity increases reaching the values measured for the ionized gas. The analysis of the stellar line-of-sight velocity distribution profile at different radii from the center allows us to explain such flat rotation velocity curves as due to the presence of stars in retrograde orbits. Resolving their kinematics the central velocity plateau disappears and two counterrotating stellar components are disentangled. In NGC 4698 the ionized gas counterrotates with respect to the inner retrograde stars. It corotates with them in IC 4889. The dynamical nature of the counterrotating component is discussed comparing the observed rotation velocity with the circular velocity inferred from the gas kinematics.