skip to main content

SciTech ConnectSciTech Connect

Title: FORMULATION OF NON-STEADY-STATE DUST FORMATION PROCESS IN ASTROPHYSICAL ENVIRONMENTS

The non-steady-state formation of small clusters and the growth of grains accompanied by chemical reactions are formulated under the consideration that the collision of key gas species (key molecule) controls the kinetics of dust formation process. The formula allows us to evaluate the size distribution and condensation efficiency of dust formed in astrophysical environments. We apply the formulation to the formation of C and MgSiO{sub 3} grains in the ejecta of supernovae, as an example, to investigate how the non-steady effect influences the formation process, condensation efficiency f{sub con,{sub ∞}}, and average radius a{sub ave,{sub ∞}} of newly formed grains in comparison with the results calculated with the steady-state nucleation rate. We show that the steady-state nucleation rate is a good approximation if the collision timescale of key molecule τ{sub coll} is much smaller than the timescale τ{sub sat} with which the supersaturation ratio increases; otherwise the effect of the non-steady state becomes remarkable, leading to a lower f{sub con,{sub ∞}} and a larger a{sub ave,{sub ∞}}. Examining the results of calculations, we reveal that the steady-state nucleation rate is applicable if the cooling gas satisfies Λ ≡ τ{sub sat}/τ{sub coll} ∼> 30 during the formation of dust, and findmore » that f{sub con,{sub ∞}} and a{sub ave,{sub ∞}} are uniquely determined by Λ{sub on} at the onset time t{sub on} of dust formation. The approximation formulae for f{sub con,{sub ∞}} and a{sub ave,{sub ∞}} as a function of Λ{sub on} could be useful in estimating the mass and typical size of newly formed grains from observed or model-predicted physical properties not only in supernova ejecta but also in mass-loss winds from evolved stars.« less
Authors:
 [1] ;  [2]
  1. Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)
  2. Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)
Publication Date:
OSTI Identifier:
22270902
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 776; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; ASTRONOMY; ASTROPHYSICS; CHEMICAL REACTIONS; COMPARATIVE EVALUATIONS; COSMIC DUST; EFFICIENCY; MAGNESIUM SILICATES; MASS TRANSFER; MOLECULES; NUCLEATION; STEADY-STATE CONDITIONS; STELLAR WINDS; SUPERNOVAE; SUPERSATURATION