The Influential Roles of Gravity, Turbulence, and Magnetic Fields in Shaping the Physical Evolution of Dense Massive Clumps

TL;DR

This study investigates how gravity, turbulence, and magnetic fields influence the evolution of dense massive clumps, finding gravity increasingly dominates at smaller scales and turbulence plays a lesser role.

Contribution

It provides new insights into the relative importance of gravity, turbulence, and magnetic fields in star-forming dense clumps, highlighting gravity's primary role.

Findings

Weak velocity dispersion-size relation (sigma ∝ L^0.11)

Turbulent energy spectrum less steep than classical turbulence

Virial parameter decreases with increasing mass, indicating stronger gravitational binding in massive clumps

Abstract

We explore the roles of the three competitors, namely, gravity, turbulence, and magnetic fields, in controlling star formation (SF) within dense, massive clumps identified in the ATLASGAL survey. By examining scaling relations, virial parameters, and turbulent energy spectra, we evaluate the dynamical state of these clumps. We observe a weak velocity dispersion-size relation (sigma proportional to L^0.11), which is much shallower than the classical Larson-like relations, suggesting that turbulence does not mainly drive internal dynamics. The turbulent energy spectrum, E(k) proportional to k^-1.21, is also less steep than what is expected for both incompressible and compressible turbulence. We equally observe a decreasing trend in the virial parameter with increasing mass (alpha_vir proportional to M^-0.37), indicating that more massive clumps are increasingly gravitationally bound. These trends indicate an increasing relative dominance of gravity over turbulence at smaller scales, aligning with multiscale collapse scenarios; however, the absolute energy balance remains unquantifiable with the current data. Although magnetic fields are not directly measured, their potential influence is considered in the interpretation of pressure balance and dynamical support. Our findings imply that gravitational processes appear to primarily regulate the structure and evolution of massive clumps.