The assembly of dusty galaxies at $z \geq 4$: statistical properties

TL;DR

This study uses cosmological simulations to explore the formation and distribution of dust in high-redshift galaxies, revealing how dust content evolves and varies in the early universe, consistent with recent ALMA observations.

Contribution

It introduces a detailed simulation approach accounting for dust production and growth, explaining observed dust properties in galaxies at redshifts $z \\geq 4$ and their spatial distribution.

Findings

Dust growth in ISM explains high dust masses at $z \\sim 4-8$.

Dust-to-metal and dust-to-gas ratios align with observational data.

Dust distribution extends from central galaxies to satellites, declining sharply beyond 30 kpc.

Abstract

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 $z \approx 4$. 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 ($\Omega_{\rm d}$) is mainly driven by stellar dust at $z \gtrsim 10$, so that mass- and metallicity-dependent yields are required to assess the dust content in the first galaxies. At $z \lesssim 9$ the growth of grains in the ISM of evolved systems (Log$(M_{\star}/M_{\odot})>8.5$) significantly increases their dust mass, in agreement with observations in the redshift range $4 \lesssim z < 8$. Our simulation shows that the variety of high redshift galaxies observed with ALMA can naturally be accounted for by modeling the grain-growth timescale as a function of the physical conditions in the gas cold phase. In addition, the trends of dust-to-metal (DTM) and dust-to-gas (${\cal D}$) ratios are compatible with the available data. A qualitative investigation of the inhomogeneous dust distribution in a representative massive halo at $z \approx 4$ shows that dust is found from the central galaxy up to the closest satellites along polluted filaments with $\rm Log({\cal D}) \leq -2.4$, but sharply declines at distances $d \gtrsim 30$ kpc along many lines of sight, where $\rm Log({\cal D}) \lesssim -4.0$.