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Session 83 - Starbursts and Mergers.
Oral session, Thursday, June 13
Union Theater,
The detection of significant populations of stars and/or gas orbiting in a retrograde manner in several spiral galaxies during the last few years has posed a daunting challenge to galaxy formation theorists, particularly because these galaxies do not show disturbed morphologies, thick disks, or other signatures of unusual kinematics. In an attempt to explain the origin of such counterrotating disks in spiral galaxies, I have developed numerical simulations which incorporate gas dynamics into a tree N-body code. I present the results of these simulations and discuss the origin of massive counterrotating disks by gas infall and spiral-dwarf mergers. I compare the simulation results from two different gas dynamics schemes: sticky particles and smoothed particle hydrodynamics (SPH). I also discuss a case-study of NGC 4138, an Sa(r) galaxy where a counterrotating disk appears to be still forming.
