The effect of stellar feedback on a Milky Way-like galaxy and its gaseous halo

We present the study of a set of N-body+smoothed particle hydrodynamics simulations of a Milky Way-like system produced by the radiative cooling of hot gas embedded in a dark matter halo. The galaxy and its gaseous halo evolve for 10 Gyr in isolation, which allows us to study how internal processes affect the evolution of the system. We show how the morphology, the kinematics and the evolution of the galaxy are affected by the input supernova feedback energy ESN, and we compare its properties with those of the Milky Way. Different values of ESN do not significantly affect the star formation history of the system, but the disc of cold gas gets thicker and more turbulent as feedback increases. Our main result is that, for the highest value of ESN considered, the galaxy shows a prominent layer of extraplanar cold (log (T/K) < 4.3) gas extended up to a few kiloparsec above the disc at column densities of 1019 cm−2. The kinematics of this material is in agreement with that inferred for the H i haloes of our Galaxy and NGC 891, although its mass is lower. Also, the location, the kinematics and the typical column densities of the hot (5.3 < log (T/K) < 5.7) gas are in good agreement with those determined from the O vi absorption systems in the halo of the Milky Way and external galaxies. In contrast with the observations, however, gas at log (T/K) < 5.3 is lacking in the circumgalactic region of our systems.