A simulation of a collapsing gas cloud falling into a Dark Matter structure (see vimeo.com/17585722 to see the Dark Matter collapsing) forming a dwarf galaxy.
This cloud is mostly neutral at the begining, but
due to the radiation from other galaxies becomes progressively more ionised as time goes on.
We can see empty regions in the neutral gas as supernovae explosions (stars exploding at the end if their lives) ionise the gas.
These are key observables for the Australian Square Kilometre Array Pathfinder.
Ultimately the gas becomes fully ionised as the galaxy forms, indicating the need for simulations to aid understanding of the extended Dark Matter
halo from the neutral hydrogen signal that the telescopes can detect.
Credit: Beard, Bourke, Crain, Duffy and GIMIC team, provided by Dr Alan Duffy, ICRAR.