IAU Symposium Abstract S186-038T
Counterrotating gas and stars
1 University of Padova, Italy, email@example.com
The phenomenon of counterrotation occurs when the angular momenta of two
different galaxian components are oriented in antiparallel way. Stars versus
gas, stars versus stars and gas versus gas have been found to be
counterrotating in a fair number of galaxies whose morphological type range
from elliptical to S0 and spiral. This kinematical decoupling
is supposed to have the same origin as the one observed in ellipticals with a
dust lane or gaseous disk along the minor axis and in polar ring galaxies,
where the angular momenta are perpendicular.
Gaseous disks counterrotating with respect to stellar disks and counterrotating
stellar disks are generally superimposed.
Gas counterrotating versus gas is found in separate regions, although
it is not excluded that in some cases gaseous disks can be apposed.
In the case of counterrotating stellar disks, they can be of different
luminosity and scale length, thus making very difficult the detection. This
fact together with the high percentage of S0 with counterrotating gas indicates
that the cause of the phenomenon, namely a second event
in the history of the galaxy, could play a relevant role in the evolution of