Garrotxa cosmological simulations of milky way-sized galaxies: general properties, hot-gas distribution, and missing baryons

We introduce a new set of simulations of Milky Way (MW)-sized galaxies using the AMR code ART + hydrodynamics in a Λ cold dark matter cosmogony. The simulation series is called GARROTXA and it follows the formation of a halo/galaxy from z = 60 to z = 0. The final virial mass of the system is ∼7.4 × 10¹¹ M _⊙. Our results are as follows. (a) Contrary to many previous studies, the circular velocity curve shows no central peak and overall agrees with recent MW observations. (b) Other quantities, such as $M\_\ast$(6 × 10¹⁰ M _⊙) and R _d (2.56 kpc), fall well inside the observational MW range. (c) We measure the disk-to-total ratio kinematically and find that D/T = 0.42. (d) The cold-gas fraction and star formation rate at z = 0, on the other hand, fall short of the values estimated for the MW. As a first scientific exploitation of the simulation series, we study the spatial distribution of hot X-ray luminous gas. We have found that most of this X-ray emitting gas is in a halo-like distribution accounting for an important fraction but not all of the missing baryons. An important amount of hot gas is also present in filaments. In all our models there is not a massive disk-like hot-gas distribution dominating the column density. Our analysis of hot-gas mock observations reveals that the homogeneity assumption leads to an overestimation of the total mass by factors of 3–5 or to an underestimation by factors of 0.7–0.1, depending on the used observational method. Finally, we confirm a clear correlation between the total hot-gas mass and the dark matter halo mass of galactic systems.