TY - JOUR

T1 - Evolution of dust grain size distribution and grain porosity in galaxies

AU - Hirashita, Hiroyuki

AU - Il’in, Vladimir B.

N1 - Publisher Copyright: © 2021 The Author(s)

PY - 2022/2/1

Y1 - 2022/2/1

N2 - The radiative properties of interstellar dust are affected not only by the grain size distribution but also by the grain porosity. We develop a model for the evolution of size-dependent grain porosity and grain size distribution over the entire history of galaxy evolution. We include stellar dust production, supernova dust destruction, shattering, coagulation, and accretion. Coagulation is assumed to be the source of grain porosity. We use a one-zone model with a constant dense gas fraction (ηdense), which regulates the balance between shattering and coagulation. We find that porosity develops after small grains are sufficiently created by the interplay between shattering and accretion (at age t ∼ 1 Gyr for star formation time-scale τSF = 5 Gyr) and are coagulated. The filling factor drops down to 0.3 at grain radii ∼ 0.03 μm for ηdense = 0.5. The grains are more porous for smaller ηdense because small grains, from which porous coagulated grains form, are more abundant. We also calculate the extinction curves based on the above results. The porosity steepens the extinction curve significantly for silicate, but not much for amorphous carbon. The porosity also increases the collisional cross-sections and produces slightly more large grains through the enhanced coagulation; however, the extinction curve does not necessarily become flatter because of the steepening effect by porosity. We also discuss the implication of our results for the Milky Way extinction curve.

AB - The radiative properties of interstellar dust are affected not only by the grain size distribution but also by the grain porosity. We develop a model for the evolution of size-dependent grain porosity and grain size distribution over the entire history of galaxy evolution. We include stellar dust production, supernova dust destruction, shattering, coagulation, and accretion. Coagulation is assumed to be the source of grain porosity. We use a one-zone model with a constant dense gas fraction (ηdense), which regulates the balance between shattering and coagulation. We find that porosity develops after small grains are sufficiently created by the interplay between shattering and accretion (at age t ∼ 1 Gyr for star formation time-scale τSF = 5 Gyr) and are coagulated. The filling factor drops down to 0.3 at grain radii ∼ 0.03 μm for ηdense = 0.5. The grains are more porous for smaller ηdense because small grains, from which porous coagulated grains form, are more abundant. We also calculate the extinction curves based on the above results. The porosity steepens the extinction curve significantly for silicate, but not much for amorphous carbon. The porosity also increases the collisional cross-sections and produces slightly more large grains through the enhanced coagulation; however, the extinction curve does not necessarily become flatter because of the steepening effect by porosity. We also discuss the implication of our results for the Milky Way extinction curve.

KW - dust, extinction

KW - galaxies: evolution

KW - galaxies: ISM

KW - ISM: evolution

KW - methods: numerical

KW - ultraviolet: ISM

UR - http://www.scopus.com/inward/record.url?scp=85131844203&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/e122df3c-9917-35b9-9a50-b7c8a44f439f/

U2 - 10.1093/mnras/stab3455

DO - 10.1093/mnras/stab3455

M3 - Article

AN - SCOPUS:85131844203

VL - 509

SP - 5771

EP - 5789

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -