Galactic Wakes: Ram Pressure Stripping in Action

Massive clusters of galaxies are about a hundred trillion times the mass of the sun.These are hostile environments for galaxies. About 10% of the mass of clusters is in the form of a hot (10 million Kelvin!), X-ray emitting plasma called the intra-cluster medium, or ICM. When galaxies fall into these environments, the drag force of the ICM, known as ram pressure, strips away gas bound to galaxies. The stripped gas forms long tails that trace their host galaxies' orbits. Eventually, galaxies lose all their gas to the ICM. Gas is the fuel to form new stars -- therefore, galaxies that live in group and cluster environments have little to no ongoing star formation, in contrast to ordinary field galaxies like the Milky Way galaxy which is actively forming stars. I use numerical simulations to create synthetic X-ray images of galactic wakes. I start with an idealized 'spherical cow' model of galactic halos, seen on the left. Trailing galactic wakes are seen on the right, after 760 million years of evolution. These simulated images are directly comparable to real X-ray images, and can help us understand the removal of gas and formation of gas wakes in real galaxies