Galaxies in a simulated ΛCDM Universe - I. Cold mode and hot cores

We study the formation of galaxies in a large volume (50 h−1 Mpc, 2 × 2883 particles) cosmological simulation, evolved using the entropy and energy-conserving smoothed particle hydrodynamics (SPH) code gadget-2. Most of the baryonic mass in galaxies of all masses is originally acquired through filamentary ‘cold mode’ accretion of gas that was never shock heated to its halo virial temperature, confirming the key feature of our earlier results obtained with a different SPH code. Atmospheres of hot, virialized gas develop in haloes above 2–3 × 1011 M⊙, a transition mass that is nearly constant from z= 3 to 0. Cold accretion persists in haloes above the transition mass, especially at z≥ 2. It dominates the growth…

• NS
  National Science Foundation

  Award: 0205969
• NA
  National Aeronautics and Space Administration

  Award: NNG04GK68G