The Young Massive Star Cluster Westerlund 2 Observed with MUSE. III. A Cluster in Motion—The Complex Internal Dynamics

Analyzing the dynamical state of nearby young massive star clusters is essential understanding cluster formation and evolution during their earliest stages. In this work we analyze stellar gas kinematics Westerlund 2 (Wd2) using data from integral field unit MUSE complement them with proper motions Gaia DR2. The mean radial velocity $15.9\,{\rm km}\,{\rm s}^{-1}$ agrees assumption that Wd2 result a cloud-cloud collision. show expansion HII region, driven by radiation many OB stars in center. profile member reveal an increasing dispersion decreasing mass low-mass five distinct groups. Based on spatial correlation cluster's two clumps, concluded imprint initial cloud collapse formed Wd2. A thorough analysis Wd2, which determines range $M_{\rm dyn,Wd2} = (7.5 \pm 1.9)\cdot10^4 - (4.4 1.1)\cdot10^5\,{\rm M}_\odot$ exceeds photometric at least factor leads to conclusion not enough remain gravitationally bound. Additionally also identify 22 runaway candidates peculiar velocities between 30 $546\,{\rm s}^{-1}$.