The problematic growth of dust in high redshift galaxies

TL;DR

This paper critically examines the hypothesis that dust growth in the diffuse interstellar medium explains dust abundance in high-redshift galaxies, finding it inadequate and suggesting supernovae as the primary dust source.

Contribution

It demonstrates the limitations of dust growth via accretion in the diffuse ISM at high redshift, emphasizing the need for supernova-produced dust to explain observations.

Findings

Dust growth in diffuse ISM is hindered by slow accretion and high temperatures.

In molecular clouds, accreted material forms icy mantles that are quickly photo-desorbed.

Supernova ejecta are likely the main source of dust in high-redshift galaxies.

Abstract

Dust growth via accretion of gas species has been proposed as the dominant process to increase the amount of dust in galaxies. We show here that this hypothesis encounters severe difficulties that make it unfit to explain the observed UV and IR properties of such systems, particularly at high redshifts. Dust growth in the diffuse ISM phases is hampered by (a) too slow accretion rates; (b) too high dust temperatures, and (c) the Coulomb barrier that effectively blocks accretion. In molecular clouds these problems are largely alleviated. Grains are cold (but not colder than the CMB temperature, (Tcmb = 20 K at redshift z=6). However, in dense environments accreted materials form icy water mantles, perhaps with impurities. Mantles are immediately photo-desorbed as grains return to the diffuse ISM at the end of the cloud lifetime, thus erasing any memory of the growth. We conclude that dust attenuating stellar light at high-$z$ must be ready-made stardust largely produced in supernova ejecta.