Title:Cosmological simulations of Milky Way-sized galaxies

Abstract:We introduce a new set of eight Milky Way-sized cosmological simulations performed using the AMR code ART + Hydrodynamics in a LCDM cosmology. The set of zoom-in simulations covers present-day virial masses in the 0.83-1.56 x 10^12 msun range and is carried out with our simple but effective deterministic star formation (SF) and ``explosive' stellar feedback prescriptions. The work is focused on showing the goodness of the simulated set of ``field' Milky Way-sized galaxies. Our results are as follows. (a) The circular velocity curves of our simulated galaxies are nearly flat. (b) Runs ending with a significant disk component, for their stellar masses, have V_max, radius, SF rate, gas fraction, and specific angular momentum values consistent with observations of late-type galaxies. (C) The two most spheroid-dominated galaxies formed in halos with late active merger histories, but other run that ends also as spheroid-dominated, never had major mergers. (d) Our simulations are consistent with the empirical stellar-to-halo mass correlation, and those that end as disk-dominated, evolve mostly along the low-mass branch of this correlation. (e) Moreover, since the last 6.5-10 Gyr, the baryonic/stellar and halo mass growth histories are proportional. (f) Within Rvir ~ 25-50% of the baryons are missed. (g) The z ~ 0 gas velocity dispersion profiles, sigma_z(r), are nearly flat and can be mostly explained by the kinetic energy injected by stars. (h) The average values of sigma_z increase at higher redshifts, following roughly the shape of the SF history.