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Wednesday 02 Dec 2020[Seminar] Star formation in chaos: can we trust simulations?

Sarah Jaffa - University of Hertfordshire

Remote seminar 14:00-15:00

Simulations test our theoretical understanding of astrophysical processes, but how far can we trust their results? Star formation involves the interplay of many complex processes including gravity, turbulence, chemistry, magnetic fields and stellar feedback, and the relative impact of each of these on the outcome of star formation is currently debated. Simulations are often pushed to their computational limit to include as many as possible, leading to very long run times. Consequently, many published works are based on only a single simulation or a handful of repeats, varying some physical parameter.

This leads us to a crisis in star formation: these chaotic systems are non-linearly dependent on the exact details of initial conditions so a single realisation cannot be taken as representative. The turbulent field used to set the initial velocity of the gas is randomly generated, and while many works have examined the effects of varying the turbulent field strength, power spectrum or solenoidal fraction, there is no comprehensive study of how the randomly generated velocities affect the star-forming activity just for different random seeds.

We have performed a suite of cloud simulations with identical setups except for the random seed used to generate the turbulent field. We show that this one change affects commonly used metrics of star formation, such as the SFE, SFR and IMF. We examine the uncertainty in these quantities when calculated from only a single simulation. This will allow larger simulations to disentangle the variation due to the parameters under investigation from the chaotic variation of turbulent initial conditions.

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