Zoom-in cosmological hydrodynamical simulation of a star-forming, barred spiral galaxy at redshift z=2

We present the results of a high-resolution zoom-in cosmological chemodynamical simulation for the formation and evolution of a star forming, barred, spiral galaxy, from the early conditions in the primordial Universe to redshift z = 2, at the peak of the cosmic star formation rate. The seed of our simulated disc galaxy is represented by the central bulge, which formed at high redshift from the interaction and coalescence of many dense, gas-rich clumps; in particular, the bulge is constituted by an X-shaped bar, in which the particles of the simulation follow "figure-of-eight" orbits as functions of time. The galaxy disc develops from redshift z =3.5, with two trailing and persistent spiral arms being present down to redshift z=1.8. The star formation activity in the galaxy happens, at all redshifts, in the bulge and in several clumps along the spiral arms, with the clumps increasing in number and size as the simulation approaches z=2. We find that stellar populations with decreasing age are concentrated towards lower galactic latitudes, being more supported by rotation, and having also lower velocity dispersion; furthermore, the stellar populations on the thin disc are the youngest and have the highest average metallicities. The specific angular momentum of the gas steadily increases as a function of redshift, at all radii on the thin disc, and the rotational velocity dispersion of the gas on the thin disc is always lower than 50 km/s, at all redshifts. Moreover, we predict that the newly-born stellar populations of the galaxy leave the spiral arms – dispersing in the galaxy disc – over a typical time scale of 193 Myr, irrespective of redshift. Finally, the pattern of the spiral arms rotates like a solid body with constant angular velocity, propagating like a perturbation on the thin disc. Our simulation may represent an important step forward in characterising the dynamics of disc galaxies at high-redshift in the era of large surveys, by making use of chemodynamical simulations, embedded in a full cosmological framework.