How do galaxies get their gas?

We examine the temperature history of gas accreted by forming galaxies in smoothed particle hydrodynamics simulations. About half of the gas follows the track expected in the conventional picture of galaxy formation, shock heating to roughly the virial temperature of the galaxy potential well (T 10 6 K for a Milky Way type galaxy) before cooling, condensing and forming stars. However, the other half radiates its acquired gravitational energy at much lower temperatures, typically T

• NS
  National Science Foundation

  Awards: 9988146, 0205969
• NA
  National Aeronautics and Space Administration