Analytic Modeling of CO Surface-Density Profiles in the M31 Molecular Clouds

Abstract

We analyze CO observations of molecular clouds in the Andromeda galaxy (M31) with a new method to derive surface-density profiles and compare directly with projected solutions of the isothermal Lane-Emden equation. The observed curvature of the surface-density profiles is consistent with the theoretical solutions. The applicability of the Lane-Emden equation indicates that the time scales of the turbulent processes responsible for an average force balance within the clouds are shorter than the time scales for the evolution of the clouds, for example toward collapse or disruption. The M31 profiles resemble those previously reported in Galactic molecular clouds suggesting similar dynamics across different environments.