A new delivery route to Galactic Nuclei: Warm halo cloud impacts
  We propose a new mechanism for the delivery of gas to the heart of galactic
nuclei. We show that warm halo clouds must periodically impact galactic centers
and potentially deliver a large (~10^{4-6} M_{solar}) mass of gas to the
galactic nucleus in a singular event. The impact of an accreting warm halo
cloud originating far in the galactic halo can, depending on mixing, produce a
nuclear starburst of low metallicity stars as well as low luminosity accretion
onto the central black hole. Based on multiphase cooling around a LambdaCDM
distribution of halos we calculate the nuclear impact rate, the mass captured
by the central black hole and the fraction of active nuclei for impacting cloud
masses in the range ~10^{4}-10^{6}M_{solar}. If there is moderate braking
during cloud infall, our model predicts an average fraction of low luminosity
active nuclei consistent with observations.
