Dust Growth by Accretion of Molecules in Supersonic Interstellar Turbulence

• Published in: The Astrophysical journal Vol. 903; no. 2; pp. 148 - 155
• Main Authors: Li, Xiang-Yu, Mattsson, Lars
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.11.2020; IOP Publishing; Institute of Physics (IOP)
• Subjects: ASTRONOMY AND ASTROPHYSICS; Astrophysics; Compressibility; Decoupling; Density distribution; Deposition; Dust; Grain growth; Grain size distribution; Interplanetary turbulence; Interstellar chemistry; Interstellar dust processes; Interstellar turbulence; Molecular clouds; Numerical simulations; Shocks; Turbulence
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/abb9ad

We show that the growth rate of dust grains in cold molecular clouds is enhanced by the high degree of compressibility of a turbulent, dilute gas. By means of high-resolution (10243) numerical simulations, we confirm the theory that the spatial mean growth rate is proportional to the gas-density variance. This also results in broadening of the grain-size distribution (GSD) due to turbulence-induced variation of the grain-growth rate. We show, for the first time in a detailed numerical simulation of hydrodynamic turbulence, that the GSD evolves toward a shape that is a reflection of the gas-density distribution, regardless of the initial distribution. That is, in case of isothermal, rotationally forced turbulence, the GSD tends to be a lognormal distribution. We also show that in hypersonic turbulence, decoupling of gas and dust becomes important and that this leads to an even further accelerated grain growth.