Dust growth by accretion of molecules in supersonic interstellar turbulence

Understand

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 towards a shape which is a reflection of the gas-density distribution, regardless of the initial distribution.