In this movie, the color of each pixel represents the temperature of the gas (blue for cold and green for hot) and the brightness of each pixel represents the density (dim for low density bright for high density). Thus diffuse and hot gas looks like a hazy green mist while cold and dense gas looks like a bright clump. Three different prescriptions for stellar feedback, the process by which newly formed stars give momentum and energy back to their environments, are employed on identical galaxy models. The center panel is our fiducial model. The rightmost is when feedback is enhanced and the leftmost is when feedback is reduced. The effect is striking, in the middle and left panels a thin disk (seen in the bottom row edge-on) forms, while in the right most panel it does not. Gas in the right most panel is also evacuated from the central region, precluding any star formation in that zone. With simulations like these we can begin to understand how the strength of feedback, when varied, can alter the shape of galaxies.
Credit: Alex Gurvich / Northwestern