Charge exchange emission and cold clumps in multi-phase galactic
  outflows
  Large-scale outflows from starburst galaxies are multi-phase, multi-component
fluids. Charge-exchange lines which originate from the interfacing surface
between the neutral and ionised components are a useful diagnostic of the cold
dense structures in the galactic outflow. From the charge-exchange lines
observed in the nearby starburst galaxy M82, we conduct surface-to-volume
analyses and deduce that the cold dense clumps in its galactic outflow have
flattened shapes, resembling a hamburger or a pancake morphology rather than
elongated shapes. The observed filamentary H$\alpha$ features are therefore not
prime charge-exchange line emitters. They are stripped material torn from the
slow moving dense clumps by the faster moving ionised fluid which are
subsequently warmed and stretched into elongated shapes. Our findings are
consistent with numerical simulations which have shown that cold dense clumps
in galactic outflows can be compressed by ram pressure, and also progressively
ablated and stripped before complete disintegration. We have shown that some
clumps could survive their passage along a galactic outflow. These are advected
into the circumgalactic environment, where their remnants would seed
condensation of the circumgalactic medium to form new clumps. The infall of
these new clumps back into the galaxy and their subsequent re-entrainment into
the galactic outflow form a loop process of galactic material recycling.
