Applicability of the Galactic density–velocity calibration in external galaxies

Determine whether the density–velocity calibration used in the Brunt–Federrath formalism for Galactic molecular clouds remains applicable to molecular clouds in an external galaxy.

Background

The Brunt–Federrath correction factor includes the exponent epsilon, which characterizes the dependence of velocity variance on density. Previous Galactic applications adopted a value of approximately 0.15, but the M33 data yield a value near 0.05, statistically consistent with zero. The paper therefore calibrates epsilon directly from the M33 cloud sample rather than assuming the Galactic value.

This leaves unresolved whether the Galactic calibration can be transferred to external galaxies. The authors assess the impact of adopting different epsilon values on the inferred solenoidal fractions, but the applicability of the Galactic density–velocity calibration itself is not established.