J/A+A/592/A18 Molecule and grain abundances (Marchand+, 2016)
Chemical solver to compute molecule and grain abundances and non-ideal MHD
resistivities in prestellar core-collapse calculations.
Marchand P., Masson J., Chabrier G., Hennebelle P., Commercon B., Vaytet N.
<Astron. Astrophys. 592, A18 (2016)>
=2016A&A...592A..18M 2016A&A...592A..18M (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium
Keywords: magnetohydrodynamics (MHD) - ISM: Molecules - stars: formation
Abstract:
We develop a detailed chemical network relevant to calculate the
conditions that are characteristic of prestellar core collapse. We
solve the system of time-dependent differential equations to calculate
the equilibrium abundances of molecules and dust grains, with a size
distribution given by size-bins for these latter. These abundances are
used to compute the different non-ideal magneto-hydrodynamics
resistivities (ambipolar, Ohmic and Hall), needed to carry out
simulations of protostellar collapse. For the first time in this
context, we take into account the evaporation of the grains, the
thermal ionisation of potassium, sodium, and hydrogen at high
temperature, and the thermionic emission of grains in the chemical
network, and we explore the impact of various cosmic ray ionisation
rates. All these processes significantly affect the non-ideal
magneto-hydrodynamics resistivities, which will modify the dynamics of
the collapse. Ambipolar diffusion and Hall effect dominate at low
densities, up to nH=1012cm-3, after which Ohmic diffusion takes
over. We find that the time-scale needed to reach chemical equilibrium
is always shorter than the typical dynamical (free fall) one. This
allows us to build a large, multi-dimensional multi-species
equilibrium abundance table over a large temperature, density and
ionisation rate ranges. This table, which we make accessible to the
community, is used during first and second prestellar core collapse
calculations to compute the non-ideal magneto-hydrodynamics
resistivities, yielding a consistent dynamical-chemical description of
this process.
Description:
chemistry.tar is the fortran code that was used to compute the
following table.
abundance.txt is a 3D table giving the abundances of several
ionised species over a wide range of density, temperature and cosmic
rays ionisation rate, useful in prestellar core collapse conditions.
The table is organised as follow : density (cm-3), temperature (K),
ionisation rate (s-1), abundance of electrons, abundances of ions
(metal (Mg etc.), molecular ions (HCO+), H3+, H+, C+, He+, K+, Na+),
abundances of grains (grains +, grain -, neutral grains) for bins 1 to
5 (see Sect. 2.4 of the paper), total abundances of grains,
integration time.
Format : '(31(e24.17,2X))'
Reading :
-------------------------------------------------------------------------
read(unit,format) nrho, nT, nX, nvar
read(unit,format)
read(unit,format)
read(unit,format)
read(unit,format)
do i=1,nX
do j=1,nT
do k=1,nrho
read(unit,format) rho(k), T(j), Xi(i), abundance(k,j,i,1:nvar)
end do
read(unit,format)
read(unit,format)
end do
read(unit,format)
read(unit,format)
end do
----------------------------------------------------------------------
The description of each column can be found in the header of the file.
You can compute the resistivities using read_table.f90, which creates
a table of resistivities with the same parameters and adding the
magnetic field dependance (see Sect. 2.1 of the paper for the formulae
used). You can use it as a subroutine in your code.
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
abund.dat 804 120000 Table of chemical abundances
abundances.txt 804 121223 Table of chemical abundances for f90
chemistry.tar 512 180 Fortran code used to compute the chemical
abundances
read_table.f90 512 18 Fortran read-table program
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Byte-by-byte Description of file: abund.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 25 E24.17 cm-3 rho Density
28- 51 E24.17 K T Temperature
54- 77 E24.17 s-1 xi Ionisation rate
80-103 E24.17 --- e Abundance of electrons
106-129 E24.17 --- Mg Abundance of ion metal (Mg, etc.)
132-155 E24.17 --- HCO+ Abundance of molecular ion HCO+
158-181 E24.17 --- H3+ Abundance of molecular ion H3+
184-207 E24.17 --- H+ Abundance of molecular ion H+
210-233 E24.17 --- C+ Abundance of molecular ion C+
236-259 E24.17 --- He+ Abundance of molecular ion He+
262-285 E24.17 --- K+ Abundance of molecular ion K+
288-311 E24.17 --- Na+ Abundance of molecular ion Na+
314-337 E24.17 --- grains+1 Abundances of grains+ for bin 1
340-363 E24.17 --- grains-1 Abundances of grains- for bin 1
366-389 E24.17 --- grains01 Abundances of grains0 for bin 1
392-415 E24.17 --- grains+2 Abundances of grains+ for bin 2
418-441 E24.17 --- grains-2 Abundances of grains- for bin 2
444-467 E24.17 --- grains02 Abundances of grains0 for bin 2
470-493 E24.17 --- grains+3 Abundances of grains+ for bin 3
496-519 E24.17 --- grains-3 Abundances of grains- for bin 3
522-545 E24.17 --- grains03 Abundances of grains0 for bin 3
548-571 E24.17 --- grains+4 Abundances of grains+ for bin 4
574-597 E24.17 --- grains-4 Abundances of grains- for bin 4
600-623 E24.17 --- grains04 Abundances of grains0 for bin 4
626-649 E24.17 --- grains+5 Abundances of grains+ for bin 5
652-675 E24.17 --- grains-5 Abundances of grains- for bin 5
678-701 E24.17 --- grains05 Abundances of grains0 for bin 5
704-727 E24.17 --- grains+t Total abundance of grains+
730-753 E24.17 --- grains-t Total abundance of grains-
756-779 E24.17 --- grains0t Total abundance of grains0
782-804 E23.17 s Tint Integration time
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Acknowledgements:
Pierre Marchand, pierre.marchand(at)ens-lyon.fr
(End) Patricia Vannier [CDS] 03-Jun-2016