The origin of dust in galaxies revisited: the mechanism determining dust content

TL;DR

This paper investigates the origins and regulation of dust in galaxies, emphasizing the balance between dust growth in molecular clouds and destruction by supernovae, and clarifies the timing of dust accumulation in galactic evolution.

Contribution

It introduces a simplified chemical evolution model that explains how dust content in galaxies is governed by a balance between accretion growth and supernova destruction, independent of stellar dust yields.

Findings

Dust in galaxies is mainly regulated by accretion in molecular clouds and supernova destruction.

The activation of dust growth occurs after a critical metal mass fraction is reached.

The solar system likely formed after significant dust accumulation in the proto-solar nebula.

Abstract

The origin of cosmic dust is a fundamental issue in planetary science. This paper revisits the origin of dust in galaxies, in particular, in the Milky Way, by using a chemical evolution model of a galaxy composed of stars, interstellar medium, metals (elements heavier than helium), and dust. We start from a review of time-evolutionary equations of the four components, and then, we present simple recipes for the stellar remnant mass and yields of metal and dust based on models of stellar nucleosynthesis and dust formation. After calibrating some model parameters with the data from the solar neighborhood, we have confirmed a shortage of the stellar dust production rate relative to the dust destruction rate by supernovae if the destruction efficiency suggested by theoretical works is correct. If the dust mass growth by material accretion in molecular clouds is active, the observed dust amount in the solar neighborhood is reproduced. We present a clear analytic explanation of the mechanism for determining dust content in galaxies after the activation of accretion growth: a balance between accretion growth and supernova destruction. Thus, the dust content is independent of the uncertainty of the stellar dust yield after the growth activation. The timing of the activation is determined by a critical metal mass fraction which depends on the growth and destruction efficiencies. The solar system formation seems to have occurred well after the activation and plenty of dust would have existed in the proto-solar nebula.