The gaseous haloes of disc galaxies
  The study of gas outside the plane of disc galaxies is crucial to understanding the circulation of material within a galaxy and between galaxies and the intergalactic environment. We present new HI observations of the edge-on galaxy NGC891, which show an extended halo component lagging behind the disc in rotation. We compare these results for NGC891 with other detections of gaseous haloes. Finally, we present a dynamical model for the formation of extra-planar gas. 
F. Fraternali (1), T. Oosterloo (2), J.J. Binney (1), R. Sancisi (3,4)   ((1) University of Oxford, (2) ASTRON, (3) INAF-Bol...