Dust formation history of galaxies: A critical role of metallicity dust mass growth by accreting materials in the interstellar medium

Abstract

This paper investigates the main driver of dust mass growth in the interstellar medium (ISM) by using a chemical evolution model of a galaxy with metals (elements heavier than helium) in the dust phase, in addition to the total amount of metals. We consider asymptotic giant branch (AGB) stars, type II supernovae (SNe II), and dust mass growth in the ISM, as the sources of dust, and SN shocks as the destruction mechanism of dust. Furthermore, to describe the dust evolution precisely, our model takes into account the age and metallicity (the ratio of metal mass to ISM mass) dependence of the sources of dust. We have particularly focused on the dust mass growth, and found that in the ISM this is regulated by the metallicity. To quantify this aspect, we introduce a "critical metallicity", which is the metallicity at which the contribution of stars (AGB stars and SNe II) equals that of the dust mass growth in the ISM. If the star-formation timescale is shorter, the value of the critical metallicity is higher, but the galactic age at which the metallicity reaches the critical metallicity is shorter. From observations, it was expected that the dust mass growth was the dominant source of dust in the Milky Way and dusty QSOs at high redshifts. By introducing a critical metallicity, it is clearly shown that the dust mass growth is the main source of dust in such galaxies with various star-formation timescales and ages. The dust mass growth in the ISM is regulated by metallicity, and we emphasize that the critical metallicity serves as an indicator to judge whether the grain growth in the ISM is the dominant source of dust in a galaxy, especially because of the strong, and nonlinear, dependence on the metallicity.

The dust content of galaxies from z = 0 to z = 9

“…This derivation is presented in detail in Asano et al (2013), and implicitly assumes spherical dust grains, a sticking coefficient α = 1 and that the solid matter in dust grains has a fixed mass density of 3 g cm −3 . This approach furthermore assumes a fixed mean grain radius of a = 0.1µm.…”

“…It is important to note that in this framework f j,cond can be approximately equal to or even smaller than fj,0 when τ exch /τacc << 1, effectively reducing the net dust growth rate to zero. We adopt an expression for the timescale for dust growth that has been used in many previous works (Hirashita 2000a;Inoue 2003;Asano et al 2013;de Bennassuti et al 2014;Schneider, Hunt & Valiante 2016) :…”

“…Dwek 1998;Hirashita, Tajiri & Kamaya 2002;Inoue 2003;Morgan & Edmunds 2003;Calura, Pipino & Matteucci 2008;Zhukovska, Gail & Trieloff 2008;Valiante et al 2009;Asano et al 2013;Calura et al 2014;Zhukovska 2014;Feldmann 2015). These models have been essential for developing our understanding of the relevance of the individual channels of dust formation to the dust content of galaxies.…”

Two-size approximation: a simple way of treating the evolution of grain size distribution in galaxies

“…Because of its metallicity dependence, accretion occurs after the ISM is enriched with metals. The metallicity level at which accretion starts to increase the dust-to-gas ratio significantly is referred to as the critical metallicity for accretion (Inoue 2011;Asano et al 2013b). Following Hirashita & Kuo (2011), we estimate the critical metallicity with βSND = βaccDs, which means that accretion starts to increase the dust-to-gas ratio more than SN destruction decreases it (equation 19; note that R ≪ βSN and that β ′ SN = βSN for α = 1).…”

“…Another important dust formation process is grain growth by the accretion of gas-phase metals in the dense ISM (Dwek 1998;Hirashita 1999 Asano et al 2013b). This process is simply referred to as accretion in this paper.…”