2004A&A...423..241S


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.20CEST07:36:46

2004A&A...423..241S - Astronomy and Astrophysics, volume 423, 241-251 (2004/8-3)

Models of gas-grain chemistry in interstellar cloud cores with a stochastic approach to surface chemistry.

STANTCHEVA T. and HERBST E.

Abstract (from CDS):

We present a gas-grain model of homogeneous cold cloud cores with time-independent physical conditions. In the model, the gas-phase chemistry is treated via rate equations while the diffusive granular chemistry is treated stochastically. The two phases are coupled through accretion and evaporation. A small network of surface reactions accounts for the surface production of the stable molecules water, formaldehyde, methanol, carbon dioxide, ammonia, and methane. The calculations are run for a time of 107 years at three different temperatures: 10K, 15K, and 20K. The results are compared with those produced in a totally deterministic gas-grain model that utilizes the rate equation method for both the gas-phase and surface chemistry. The results of the different models are in agreement for the abundances of the gaseous species except for later times when the surface chemistry begins to affect the gas. The agreement for the surface species, however, is somewhat mixed. The average abundances of highly reactive surface species can be orders of magnitude larger in the stochastic-deterministic model than in the purely deterministic one. For non-reactive species, the results of the models can disagree strongly at early times, but agree to well within an order of magnitude at later times for most molecules. Strong exceptions occur for CO and H2CO at 10K, and for CO2 at 20K. The agreement seems to be best at a temperature of 15K. As opposed to the use of the normal rate equation method of surface chemistry, the modified rate method is in significantly better agreement with the stochastic-deterministic approach. Comparison with observations of molecular ices in dense clouds shows mixed agreement.

Abstract Copyright:

Journal keyword(s): ISM: abundances - ISM: molecules - molecular processes

CDS comments: Table 1 : Elias 16 = Elia 3-16.

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 Kim 1-38 * 04 39 38.8673861844 +26 11 26.630421918           K1III 124 0
2 NAME Cha I MoC 11 06 48 -77 18.0           ~ 985 1
3 OTS 18 IR 11 09 36.6 -76 33 39           ~ 8 0
4 W 33a Y*O 18 14 39.0 -17 52 03           ~ 587 0
5 [EC89] SVS 4-5 Y*O 18 29 57.59 +01 13 00.6           ~ 30 1
6 NAME Serpens SVS 4 IR Cluster Cl* 18 29 57.84 +01 12 48.1           ~ 38 1
7 2MASS J18295785+0112514 Y*O 18 29 57.858 +01 12 51.40           ~ 58 3
8 RAFGL 7009S HII 18 34 20.911 -05 59 42.23           ~ 195 0

    Equat.    Gal    SGal    Ecl

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2020.10.20-07:36:46

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