Three-dimensional evolution of worms and chimneys in the Galactic disc

Three-dimensional modelling of the flow of gas and plasma in a section of the Galaxy has been carried out to study the evolution and formation of Galactic chimneys and worms. It is found that clustered supernovae located on either side of the Galactic plane are sources for the formation of well-collimated chimneys, having widths of similar to 150-200 pc. The thick gas disc may have a role in the collimation of chimneys. Channel maps of disc gas, obtained from the simulations, show the presence of sheet-like structures running perpendicular to the Galactic plane and resembling worms. Worms are believed to result from the break-up of the shells and supershells. However, the simulations show that although some worms correlate well with the debris of broken shells/supershells, others do not. They are cold gas that has been accelerated in the disc and rise on to the thick gas disc.