A mushroom-shaped structure from the impact of a cloud with the Galactic disk*
Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada e-mail: email@example.com
Accepted: 3 May 2004
We propose that the mushroom-shaped structure of the Galactic worm GW 123.4-1.5 is created by a cloud collision with the Galactic gas disk. A hydrodynamic simulation shows that a mushroom-shaped structure is created after the cloud crosses the Galactic midplane. The lifetime of the mushroom-shaped structure is of order the dynamical time scale of the disk, years. We find that the velocities across the cap of the mushroom-shaped structure in the simulation are consistent with the observed values. The simulation also predicts a structure on the opposite side of the Galactic plane which is created by the Kelvin-Helmholtz instability after the cloud passes through the disk.
Key words: Galaxy: structure / ISM: clouds / ISM: individual: GW 123.4-1.5 / ISM: structure
© ESO, 2004