Cooling flows within galactic haloes: The kinematics and properties of infalling multiphase gas

Abstract

We study the formation of discs via the cooling flow of gas within galactic haloes using smoothed particle hydrodynamic simulations. These simulations resolve mass scales of a few thousand solar masses in the gas component for the first time. Thermal instabilities result in the formation of numerous warm clouds that are pressure confined by the hot ambient halo gas. The clouds fall slowly on to the disc through non-spherical accretion from material flowing preferentially down the angular momentum axis. The rotational velocity of the infalling cold gas decreases as a function of height above the disc, closely resembling that of the extra-planar gas recently observed around the spiral galaxy, NGC 891. © 2006 RAS.