The Dynamical State of Massive Clumps

TL;DR

This study uses synthetic observations to analyze the kinematic properties of massive star-forming clumps, revealing how observational estimates relate to true 3D properties and their implications for understanding star formation dynamics.

Contribution

It introduces a method to compare synthetic line profiles with 3D simulation data, highlighting the effects of observational limitations on derived physical parameters.

Findings

Velocity dispersion from N2H+ lines estimates 3D clump dispersion well.

Mass relation between 3D clumps and synthetic sources shows large scatter.

Virial parameters are not strongly correlated with clump mass in 3D data.

Abstract

The dynamical state of massive clumps is key to our understanding of the formation of massive stars. In this work, we study the kinematic properties of massive clumps using synthetic observations. We have previously compiled a very large catalog of synthetic dust-continuum compact sources from our 250 pc, SN-driven, star formation simulation. Here, we compute synthetic $\rm N_{2}H^{+}$ line profiles for a subsample of those sources and compare their properties with the observations and with those of the corresponding three-dimensional (3D) clumps in the simulation. We find that the velocity dispersion of the sources estimated from the $\rm N_{2}H^{+}$ line is a good estimate of that of the 3D clumps, although its correlation with the source size is weaker than the velocity-size correlation of the 3D clumps. The relation between the mass of the 3D clumps, $M_{\rm main}$, and that of the corresponding synthetic sources, $M_{\rm SED}$, has a large scatter and a slope of 0.5, $M_{\rm main} \propto M_{\rm SED}^{0.5}$, due to uncertainties arising from the observational band-merging procedure and from projection effects along the line of sight. As a result, the virial parameters of the 3D clumps are not correlated with the clump masses, even if a negative correlation is found for the compact sources, and the virial parameter of the most massive sources may significantly underestimate that of the associated clumps.