Determine the turbulent-gas correlation time and its gas-fraction dependence

Determine the correlation time of the stochastic gas forcing in turbulent, gas-rich galactic discs and characterize how that correlation time depends on the gas fraction, in order to assess the validity of the white-noise approximation used in the Langevin model of bar onset.

Background

The paper models the effect of turbulent gas on the growth of the stellar bar through a Langevin equation in which the gas supplies stochastic forcing. Treating this forcing as white noise requires the correlation time multiplied by the bar growth rate to be much less than one.

The authors explicitly state that the relevant correlation time and its dependence on gas fraction were not measured in the simulations. Determining them would establish whether the white-noise treatment is physically justified and how stochastic forcing varies across gas-rich disc models.

References

It assumes white noise, which requires $\tau_{\rm corr}\gamma_\star\ll1$, and neither $\tau_{\rm corr}$ nor its dependence on $f_{\rm gas}$ has been measured here.

— Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars  (2609.03275 - Bland-Hawthorn et al., 3 Sep 2026) in Section 4, subsection “Bar onset in a fluctuating disc”