Chad Bustard 
Postdoctoral Fellow @ Kavli Institute for Theoretical Physics (KITP)

How galaxies form and evolve is an unsolved problem in cosmology. The cycle of gas in and out of galaxies is crucial for our understanding, but it is an extremely complex, multi-scale process. One critical component of the gas cycle is galactic winds, which help to regulate galaxy growth by displacing gas from star-forming sites and driving it into the circumgalactic medium. These winds are driven by collections of exploding stars (supernovae), which energize a galaxy's interstellar medium. These drive turbulence and shocks, and if energetic enough, launch outflows of material that can escape the galaxy's gravitational pull. To fully understand this process, observers and theorists work together to determine the composition of these winds, how they are launched out of their host galaxies, and how they affect the surrounding circumgalactic medium, which is believed to harbor a large fraction of the baryons in the galactic ecosystem. 

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I research through both analytic studies and large-scale simulations how these winds are launched, how they compare to observations, and how they influence the galaxy's surroundings. An important piece may be the pressure support from cosmic rays, the most energetic particles in the Universe, whose transport along magnetic field lines is mediated by scattering off plasma waves. The visualizations below show simulated cosmic ray driven winds from the Large Magellanic Cloud (LMC). This dwarf satellite galaxy of the Milky Way is simultaneously launching outflows and being ram pressure stripped by its infall into the Milky Way halo. In these magnetohydrodynamic (MHD) simulations, cosmic rays are crucial for driving extended winds and fountains, and they form a significant halo around the LMC.

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