Old stellar counter-rotating components in early-type galaxies from elliptical-spiral mergers
LERMA, UMR 8112, CNRS, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France e-mail: [paola.dimatteo;francoise.combes]@obspm.fr
2 Université Pierre et Marie Curie – Paris 6, 4 place Jussieu, 75252 Paris Cedex 5, France e-mail: [anne-laure.melchior;benoit.semelin]@obspm.fr
Accepted: 30 September 2007
We use numerical simulations to investigate the possibility of forming counter-rotating old stellar components by major mergers between an elliptical and a spiral galaxy. We show that counterrotation can appear both in dissipative and dissipationless retrograde mergers, and it is mostly associated to the presence of a disk component, which preserves part of its initial spin. In turn, the external regions of the two interacting galaxies acquire part of the orbital angular momentum, from the action of tidal forces exerted on each galaxy by the companion.
Key words: galaxies: general / galaxies: interactions / galaxies: kinematics and dynamics / galaxies: formation / galaxies: structure
© ESO, 2007