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Molecular Clouds as Gravitational Instabilities in Rotating Disks: A Modified Stability Criterion by Meidt, Sharon E. is a scholarly article available to read on EtoBox.

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Molecular gas disks are generally Toomre stable ($Q_T>$1) and yet clearly gravitationally unstable to structure formation as evidenced by the existence of molecular clouds and ongoing star formation. This paper adopts a 3D perspective to obtain a general picture of instabilities in flattened rotating disks, using the 3D dispersion relation to describe how disks evolve when perturbed over their vertical extents. By explicitly adding a vertical perturbation to an unperturbed equilibrium disk, stability is shown to vary with height above the mid-plane. Near to $z$=0 where the equilibrium density is roughly constant, instability takes on a Jeans-like quality, occurring on scales larger than the Jeans length and subject to a threshold $Q_M=\kappa^2/(4\pi G\rho)=1$ or roughly $Q_T\approx 2$. Far from the mid-plane, on the other hand, stability is pervasive, and the threshold for the total disk (out to $z=\pm\infty$) to be stabilized is lowered to $Q_T=1$ as a consequence. In this new framework, gas disks are able to fragment through partial 3D instability even where total 2D instability is suppressed. The growth rates of the fragments formed via 3D instability are comparable to, or faste

Author

Meidt, Sharon E.

Published

2022

Language

EN