COSMOLOGICAL SIMULATIONS OF MILKY WAY-SIZED GALAXIES

We introduce a new set of eight Milky Way-sized cosmological simulations performed using the AMR code Adaptive Refinement Tree + Hydrodynamics in Lambda CDM cosmology. The set of zoom-in simulations covers present-day virial masses that range from 8.3 x 10(11) M-circle dot to 1.56 x 10(12) M-circle dot and is carried out with our simple but effective prescriptions for deterministic star formation (SF) and explosive stellar feedback. The work focuses on showing the goodness of the simulated set of field Milky Way-sized galaxies. To this end, we compare some of the predicted physical quantities with the corresponding observed ones. Our results are as follows. (a) In agreement with some previous works, we found curves of circular velocity that are flat or slightly peaked. (b) All simulated galaxies with a significant disk component are consistent with the observed Tully-Fisher, radius-mass, and cold gas-stellar mass correlations of late-type galaxies. (c) The disk-dominated galaxies have stellar specific angular momenta in agreement with those of late-type galaxies, with values around 103 km s(-1) kpc(-1). (d) The SF rates at z = 0 of all runs but one are comparable to those estimated for the star-forming galaxies. (e) The two most spheroid-dominated galaxies formed in halos with late active merger histories and late bursts of SF, but the other run that ends also dominated by a spheroid never had major mergers. (f) The simulated galaxies lie in the semi-empirical correlation of stellar to halo mass of local central galaxies, and those that end up as disk-dominated evolve mostly along the low-mass branch of this correlation. Moreover, the growth histories of baryonic and stellar mass of these galaxies are proportional to their growth histories of halo mass over the last 6.5-10 Gyr. (g) Within the virial radii of the simulations, approximate to 25%-50% of the baryons are missed; the amount of gas in the halo is similar to the amount in stars in the galaxy, and most of this gas is in the warm-hot phase. (h) The profiles of z similar to 0 vertical gas velocity dispersion, sigma(z)(r), are nearly flat and can be mostly explained by the kinetic energy injected by stars. The average values of sigma(z) increase at higher redshifts, following roughly the shape of the SF history.