J/A+A/502/845 Dust coagulation in molecular clouds (Ormel+, 2009)
Dust coagulation and fragmentation in molecular clouds:
I. How collisions between dust aggregates alter the dust size distribution.
Ormel C.W., Paszun D., Dominik C., Tielens A.G.G.M.
<Astron. Astrophys. 502, 845 (2009)>
=2009A&A...502..845O 2009A&A...502..845O
ADC_Keywords: Molecular clouds ; Interstellar medium ; Models
Keywords: ISM: dust, extinction - ISM: clouds - turbulence - methods: numerical
Abstract:
The cores in molecular clouds are the densest and coldest regions of
the interstellar medium (ISM). In these regions ISM-dust grains have
the potential to coagulate. This study investigates the collisional
evolution of the dust population by combining two models: a binary
model that simulates the collision between two aggregates and a
coagulation model that computes the dust size distribution with time.
In the first, results from a parameter study quantify the outcome of
the collision - sticking, fragmentation (shattering, breakage, and
erosion) - and the effects on the internal structure of the particles
in tabular format. These tables are then used as input for the dust
evolution model, which is applied to an homogeneous and static cloud
of temperature 10K and gas densities between 103 and 107cm-3.
Description:
Quantities (Q) provided in the tables are (see Table 1 of the paper):
Q=fmiss fraction of missing collisions
Q=Nfk number of fragments in the large component
Q=Sf standard deviation in Nf
Q=fpwl fraction of mass in the power-law component
Q=q slope in the power-law component
Q=Cphi change in the filling factor of the large particle component
These output quantities are sampled as function of
1. Recipe type: 'Global' or 'Local'
2. Normalized impact parameter
3. Dimensionless energy parameter eps, which is the collision energy
divided by a critical energy threshold
4. The initial filling factor of the aggregate (phi) OR, in case of
Q=fmiss, the ratio of the outer over the geometrical radius (Ra).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
recip1.dat 85 90 Collision recipe data for 4 ratio of the outer
over the geometrical radius (Ra=aout/asigma)
recip2.dat 90 450 Collision recipe data for 4 initial filling
factor of the aggregate (phi)
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Byte-by-byte Description of file: recip1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Recipe Recipe (GLOBAL or LOCAL)
8- 12 F5.3 --- b Normalized impact parameter (b/b_max)
14- 18 A5 --- Q [fmiss] Parameter name (G1)
20- 29 E10.4 ---- eps Dimensionless energy value (G2)
31- 36 F6.4 --- Ra1 First ratio of the outer over the geometrical
radius value
38- 43 F6.4 --- Q1 Value of quantity Q at Ra=Ra1
45- 50 F6.4 --- Ra2 Second ratio of the outer over the geometrical
radius value
52- 57 F6.4 --- Q2 Value of quantity Q at Ra=Ra2
59- 64 F6.4 --- Ra3 Third ratio of the outer over the geometrical
radius value
66- 71 F6.4 --- Q3 Value of quantity Q at Ra=Ra3
73- 78 F6.4 --- Ra4 Fourth ratio of the outer over the geometrical
radius value
80- 85 F6.4 --- Q4 Value of quantity Q at Ra=Ra4
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Byte-by-byte Description of file: recip2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Recipe Recipe (GLOBAL or LOCAL)
8- 12 F5.3 --- b Normalized impact parameter (b/b_max)
14- 17 A4 --- Q Q parameter designation (G1)
19- 28 E10.4 ---- eps Dimensionless energy value (G2)
30- 35 F6.4 --- phi1 First different initial filling factor value
37- 43 F7.4 --- Q1 Value of quantity Q at phi=phi1
45- 50 F6.4 --- phi2 Second different initial filling factor value
52- 59 F8.4 --- Q2 Value of quantity Q at phi=phi2
61- 66 F6.4 --- phi3 Third different initial filling factor value
68- 75 F8.4 --- Q3 Value of quantity Q at phi=phi3
77- 82 F6.4 --- phi4 Fourth different initial filling factor value
84- 90 F7.4 --- Q4 Value of quantity Q at phi=phi4
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Global notes:
Note (G1): Quantities studied are:
fmiss = fraction of missing collisions
Nf = number of fragments in the large component
Sf = standard deviation in Nf
fpwl = fraction of mass in the power-law component, normalized to
Ntot (global recipe) or Nµ (local recipe)
q = slope in the power-law component
Cphi = change in the filling factor of the large particle component
Note (G2): Dimensionless energy parameter. This is the collision energy
E=(1/2)µ.v2 divided by a critical energy Ecrit.
See Equation (13) and Table 1 in the paper for its definition.
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Acknowledgements:
Chris W. Ormel, ormel(at)mpia-hd.mpg.de
(End) C.W. Ormel [MPIA], Patricia Vannier [CDS] 18-Jun-2009