Figure 2: Evolution of the SO_{2}, SO, H_{2}S, OCS and CS abundances with respect to H_{2} as a function of time, for the three pre-evaporation gas phase compositions A ( left panels), B ( central panels), and C ( right panels) and the four grain mantle compositions (1 to 4, from the top to the bottom). The gas temperature is 100 K and the H_{2} density is 10^{7} cm^{-3}. | |
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Figure 3: Evolution of the SO_{2}, SO, H_{2}S, OCS and CS abundances with respect to H_{2} as a function of time, using pre-evaporated gas phase composition A and the four grain mantle mixtures (1 to 4, from the top to the bottom). The gas temperature is 100 K and the density is 10^{5} cm^{-3} ( a) left panels), 10^{6} cm^{-3} ( b) central panels) and 10^{7} cm^{-3} ( c) right panels). | |
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Figure 4: Same as Fig. 3 but with a temperature of 300 K. | |
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Figure 5: Evolution of the abundance ratios SO_{2}/SO ( upper panels), SO_{2}/H_{2}S ( middle panels) and OCS/H_{2}S ( lower panels) as functions of time for composition A, a gas temperature of 100 K, and densities of 10^{5} cm^{-3} ( left panels), 10^{6} cm^{-3} ( central panels) and 10^{7} cm^{-3} ( right panels). The solid, dashed-dotted, dashed, and dotted lines represent results from models 1, 2, 3, and 4, respectively. In the upper panels, the results of model 2 and 4 are the same and represented by dashed-dotted lines. | |
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Figure 6: Same as Fig. 5 but with a temperature of 300 K. | |
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Figure 7: Comparison between the observed ratios SO_{2}/SO, SO_{2}/H_{2}S and OCS/H_{2}S towards IRAS 16293-2422 and the theoretical predictions of four models (Mod. 1, 2, 3 and 4; all with composition A) for a gas temperature of 100 K and a density of 10^{7} cm^{-3}. The grey empty boxes, if shown, represent those instances in which particular calculated ratios are in agreement for a range of times with the observed ones taking into account the uncertainties in the observations. The grey filled box for model 2 shows the time interval where all calculated ratios are in agreement with the observed ones. | |
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Figure 1: The "variation'' (see text) of the abundances of SO, H_{2}S, and CS divided by the amplitude ( ) of the perturbation of the rate coefficients plotted for reactions with number between 86 and 834; i.e., all the reactions in the model exept those dealing with dust grains. The numbers indicate those reactions that induce a variation of more than 5% of the highest variation for each species. | |
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