Massive Star Forming Regions: Turbulent Support or Global Collapse?

TL;DR

This study provides numerical evidence that high-mass star forming regions are likely undergoing global gravitational collapse, with observed velocity dispersions mainly caused by infall motions rather than turbulence.

Contribution

It demonstrates through simulations that high-mass star forming regions can arise from gravitational infall, challenging the turbulence-supported equilibrium model.

Findings

Clumps have sizes ~1 pc, masses of several hundred solar masses, and velocity dispersions ~3 km/s.

Cores are ~0.1 pc, densities ~10^5, masses 2-300 solar masses, matching observed distributions.

Results suggest high-mass star forming regions are in global collapse, not turbulence-supported equilibrium.

Abstract

We present preliminary numerical evidence that the physical conditions in high-mass star forming regions can arise from global gravitational infall, with the velocity dispersions being caused primarily by infall motions rather than random turbulence. To this end, we study the clumps and cores appearing in the region of central collapse in a numerical simulation of the formation, evolution, and subsequent collapse of a dense cloud out of a transonic compression in the diffuse atomic ISM. The clumps have sizes $\sim 1$ pc, masses of several hundred $M_\odot$, and three-dimensional velocity dispersions $\sim 3$ km s$^{-1}$, in agreement with typical observed values for such structures. The clumps break down into massive cores of sizes $\sim 0.1$ pc, densities $\sim 10^5$, masses 2-300 $M_\odot$, with distributions of these quantities that peak at the same values as the massive core sample in a recent survey of the Cygnus X molecular cloud complex. Although preliminary, these results suggest that high-mass star forming clumps may be in a state of global gravitational collapse rather than in equilibrium supported by strong turbulence.