Chemical Models: Where to Start from?

Abstract

Chemical models are sensitive to the adopted set of initial input parameters. One of these crucial parameters is the set of the adopted gas-phase elemental abundances with which the reactions networks start to operate. Based on the most recent observations and theoretical data, we investigate the effect of initial abundance variation on both gas-phase and gas-grain chemical models. At early-time stages less than 1 Myr, there is little difference between results with different initial [C]/[O] ratios. This holds for gas-phase and gas-grain models. At later evolutionary time or in the steady state, the result of the gas-grain model shows little or no difference due to variations of the initial [C]/[O] ratios. On the contrary, at the late or at steady state times, the abundances of chemical species using gas-phase models are very sensitive to any variation of the initial [C]/[O] ratios.