IAU Symposium Abstract S186-025T

Extended gas in interacting systems

F. Combes
Observatoire de Paris, DEMIRM, Paris, France bottaro@obspm.fr

Since the gas component is much more radially extended than the stellar component in a spiral galaxy, it is more perturbed during interactions; there can be very long tidal tails, huge splashes of gas as far as hundreds kpc away. In the same time, gravity torques and dissipation drive the gas inwards, and gas concentration is higher in interacting galaxies and mergers. What is the fate of the perturbed gas? The bulk of it is bound to rain down on the galaxies, on time scales of Gyrs. Some of it will be caught in quasi-equilibrium structures such as polar rings, that are widely studied as probes of the dark matter potential. The gas infall is also one of the main mechanisms to maintain warps. The most recent observations will be reviewed to show the role of gas infall in the evolution of galaxies: bar instability, star formation, disk thickness... The outer parts of galaxies appear to never reach gravitational stability, and their dynamics will be discussed.