J/A+A/568/A91 Gas opacity in circumstellar environments (Malygin+, 2014)
Mean gas opacity for circumstellar environments and equilibrium temperature
degeneracy.
Malygin M.G., Kuiper R., Klahr H., Dullemond C.P., Henning T.
<Astron. Astrophys. 568, A91 (2014)>
=2014A&A...568A..91M 2014A&A...568A..91M
ADC_Keywords: Interstellar medium ; Models
Keywords: opacity - radiative transfer - methods: numerical
Abstract:
In a molecular cloud dust opacity typically dominates over gas
opacity, yet in the vicinities of forming stars dust is depleted, and
gas is the sole provider of opacity. In the optically thin
circumstellar environments the radiation temperature cannot be assumed
to be equal to the gas temperature, hence the two-temperature Planck
means are necessary to calculate the radiative equilibrium.
By using the two-temperature mean opacity one does obtain the proper
equilibrium gas temperature in a circumstellar environment, which is
in a chemical equilibrium. A careful consideration of a radiative
transfer problem reveals that the equilibrium temperature solution can
be degenerate in an optically thin gaseous environment.
We compute mean gas opacities based on the publicly available code
DFSYNTHE by Kurucz and Castelli. We performed the calculations
assuming local thermodynamic equilibrium and an ideal gas equation of
state. The values were derived by direct integration of the
high-resolution opacity spectrum.
Description:
The tables contain frequency averaged gas opacity for a wide range of
gas temperatures and pressures as well as for three different
metallicities. The first table contains Rosseland and Planck means.
The second table consists two-temperature Planck means, which can be
used when the radiation temperature is different from the gas
temperature, but a chemical equilibrium can be assumed. To be used in
radiative transfer modelling.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 35532 Rosseland and Planck means for 94 temperatures,
126 pressures and 3 metallicities
table2.dat 52 355320 Two-temperature Planck means for 94 temperatures
126 pressures, 3 metallicities and
10 radiation temperatures
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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2- 5 F4.1 [Sun] [Me/H] [-0.3/0.3] Metallicity (-0.3, 0.0, +0.3 ) (G1)
7- 13 I7 K Tgas [700/1e06] Gas temperature Tgas
15- 23 E9.4 dPa Pgas [1e-09/7.2e+08] Gas pressure Pgas (dyn/cm2)
25- 33 E9.4 g/cm3 rho Gas density ρ
35- 46 E12.6 cm2/g kR Rosseland mean opacity κR
48- 59 E12.6 cm2/g kP Planck mean opacity κP
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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2- 5 F4.1 [Sun] [Me/H] [-0.3/0.3] Metallicity (-0.3,0.0,+0.3) (G1)
7- 11 I5 K Trad [3000/50000] Radiation temperature Trad
13- 19 I7 K Tgas [700/1e+06] Gas temperature Tgas
21- 29 E9.4 dPa Pgas [1e-09/7.2e+08] Gas pressure Pgas (dyn/cm2)
31- 39 E9.4 g/cm3 rho Gas density ρ
41- 52 E12.6 cm2/g kP Two-temperature Planck mean opacity
κP(Trad,Tgas)
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Global notes:
Note (G1): metallicity [Me/H] is a logarithm base 10 of the multiplicative
factor applied to atomic abundances of all the species but H and He.
The reference abundances (i.e. for [Me/H]=+0.0) are from Grevesse & Sauval
(1998SSRv...85..161G 1998SSRv...85..161G)
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Acknowledgements:
Mykola Malygin, malygin(at)mpia.de
References:
Grevesse & Sauval, 1998SSRv...85..161G 1998SSRv...85..161G, Standard Solar Composition
History:
* 26-Aug-2014 : on-line data
* 27-Aug-2014 : tables 1 and 2 corrected (from author)
(End) Mykola Malygin [MPIA, Heidelberg], Patricia Vannier [CDS] 28-Jul-2014