2020MNRAS.494.1071G

The recent discovery of high-redshift dusty galaxies implies a rapid dust enrichment of their interstellar medium (ISM). To interpret these observations, we run a cosmological simulation in a 30 h^–1 cMpc/size volume down to z ≃ 4. We use the hydrodynamical code DUSTYGADGET, which accounts for the production of dust by stellar populations and its evolution in the ISM. We find that the cosmic dust density parameter (Ω_d) is mainly driven by stellar dust at z >= 10, so that mass- and metallicity-dependent yields are required to assess the dust content in the first galaxies. At z <= 9, the growth of grains in the ISM of evolved systems [log(M_*/M_☉) > 8.5] significantly increases their dust mass, in agreement with observations in the redshift range 4 <= z < 8. Our simulation shows that the variety of high-redshift galaxies observed with the Atacama Large Millimeter Array can naturally be accounted for by modelling the grain growth time-scale as a function of the physical conditions in the gas cold phase. In addition, the trends of dust-to-metal and dust-to-gas ( D) ratios are compatible with the available data. A qualitative investigation of the inhomogeneous dust distribution in a representative massive halo at z ≃ 4 shows that dust is found from the central galaxy up to the closest satellites along polluted filaments with log( D) ≤-2.4, but sharply declines at distances d >= 30 kpc along many lines of sight, where log( D) ≲-4.0.