J/ApJ/812/142 Chemical evolution in the LMC with a new model (Acharyya+, 2015)
Molecular development in the Large Magellanic Cloud.
Acharyya K., Herbst E.
<Astrophys. J., 812, 142 (2015)>
=2015ApJ...812..142A 2015ApJ...812..142A (SIMBAD/NED BibCode)
ADC_Keywords: Abundances ; Models ; Magellanic Clouds
Keywords: astrochemistry; ISM: molecules; molecular processes
Abstract:
Using a new network and a new model, we have studied chemical
complexity in cold portions of dense clouds of the Large Magellanic
Cloud (LMC). We varied the hydrogen number density between 1x105 and
5x105/cm3 and, for each density, we ran models for AV=3, 5, and
10. Then, for each density and visual extinction we varied the grain
temperature between 10 and 50K in small intervals, while keeping the
gas temperature constant at 20K. We used a gas-to-dust mass ratio
based on a variety of observations and analyses, and scaled the
elemental abundances of the LMC so that they are representative of
so-called "low" metallic abundances. We found that although the LMC is
metal-poor, it still shows a rich chemistry; almost all the major
observed species in the gas phase of our Galaxy should be detectable
using present-day observational facilities. We compared our model
results with observed gas-phase abundances in some cold and dense
sources, and found reasonably good agreement for most species. We also
found that some observed results, especially for methanol, are better
matched if these regions currently possess lower temperatures, or
possessed them in the past. Finally, we discussed our simulated
abundances for H2O ice with respect to total hydrogen, and CO2,
CO, CH3OH, and NH3 ices with respect to water ice, and compared
our values with those for two observed ices --CO2 and CO-- detected
in front of young stellar objects in the LMC.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table7.dat 193 261 Abundances of assorted species as a function of
various parameters
--------------------------------------------------------------------------------
See also:
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 E3.0 cm-3 NH [100000/500000] Hydrogen number density
5- 6 I2 mag Av [3/10] The visual extinction AV
8- 13 A6 --- Species Species identifier
15- 22 E8.2 --- A1e4-10 Species abundance at 1e4yr and 10K
24- 31 E8.2 --- A1e4-20 Species abundance at 1e4yr and 20K
33- 40 E8.2 --- A1e4-30 Species abundance at 1e4yr and 30K
42- 49 E8.2 --- A1e4-40 Species abundance at 1e4yr and 40K
51- 58 E8.2 --- A1e4-50 Species abundance at 1e4yr and 50K
60- 67 E8.2 --- A5e4-10 Species abundance at 5e4yr and 10K
69- 76 E8.2 --- A5e4-20 Species abundance at 5e4yr and 20K
78- 85 E8.2 --- A5e4-30 Species abundance at 5e4yr and 30K
87- 94 E8.2 --- A5e4-40 Species abundance at 5e4yr and 40K
96-103 E8.2 --- A5e4-50 Species abundance at 5e4yr and 50K
105-112 E8.2 --- A1e5-10 Species abundance at 1e5yr and 10K
114-121 E8.2 --- A1e5-20 Species abundance at 1e5yr and 20K
123-130 E8.2 --- A1e5-30 Species abundance at 1e5yr and 30K
132-139 E8.2 --- A1e5-40 Species abundance at 1e5yr and 40K
141-148 E8.2 --- A1e5-50 Species abundance at 1e5yr and 50K
150-157 E8.2 --- A5e5-10 Species abundance at 5e5yr and 10K
159-166 E8.2 --- A5e5-20 Species abundance at 5e5yr and 20K
168-175 E8.2 --- A5e5-30 Species abundance at 5e5yr and 30K
177-184 E8.2 --- A5e5-40 Species abundance at 5e5yr and 40K
186-193 E8.2 --- A5e5-50 Species abundance at 5e5yr and 50K
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Feb-2016