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
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2 Dipartimento di Astronomia, Universit\`a di Padova, Italy
< bertola,corsini,firstname.lastname@example.org >
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
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.