Long-duration simulations of the evolution of jet-driven molecular outflows

We use numerical simulations to examine the mass-velocity, $m(v)$, and intensity-velocity, $I(v)$, relations in jet-driven molecular outflows up to an age of 2300 yr. We find that the $m(v)$ relation is a power-law, $m(v) \propto v^{-\gamma}$, the exponent of which increases with time up to $\gamma \approx 1.6$ at $t \approx 1500$ yr. It then becomes roughly constant. This indicates that γ does not evolve throughout the lifetime of a molecular outflow, at least in the context of the jet-driven model. We also investigate the effect of long-period episodicity of the jet on the $m(v)$ and $I(v)$ relations. We find that, contrary to previous expectations, these relations are not significantly changed with the introduction of such variability into the jet. Finally, we present a novel, and relatively simple, parallelisation method for the code used in these simulations. This gives an increase of roughly a factor of 4 in speed over standard methods, and allows the simulations presented here to be run fairly easily, even with modest computational resources.