Fountain-driven gas accretion by the Milky Way
  Accretion of fresh gas at a rate of ~ 1 M_{sun} yr^{-1} is necessary in star-forming disc galaxies, such as the Milky Way, in order to sustain their star-formation rates. In this work we present the results of a new hydrodynamic simulation supporting the scenario in which the gas required for star formation is drawn from the hot corona that surrounds the star-forming disc. In particular, the cooling of this hot gas and its accretion on to the disc are caused by the passage of cold galactic fountain clouds through the corona. 
F. Marinacci, F. Fraternali, J. Binney, C. Nipoti, L. Ciotti, P.   Londrillo
astro-ph.GA