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We present the kinematic anaylsis of $246$ stars within $4^\prime$ from thecenter of Orion Nebula Cluster (ONC), the closest massive star cluster withactive star formation across the full mass range, which provides valuableinsights in the the formation and evolution of star cluster on anindividual-star basis. High-precision radial velocities and surfacetemperatures are retrieved from spectra acquired by the NIRSPEC instrument usedwith adaptive optics (NIRSPAO) on the Keck II 10-m telescope. Athree-dimensional kinematic map is then constructed by combining with theproper motions previously measured by the Hubble Space Telescope (HST)ACS/WFPC2/WFC3IR and Keck II NIRC2. The measured root-mean-squared velocitydispersion is $2.26\pm0.08~\mathrm{km}\,\mathrm{s}^{-1}$, significantly higherthan the virial equilibrium's requirement of$1.73~\mathrm{km}\,\mathrm{s}^{-1}$, suggesting that the ONC core issupervirial, consistent with previous findings. Energy equipartition is notdetected in the cluster. Most notably, the velocity of each star relative toits neighbors is found to be negatively correlated with stellar mass. Low-massstars moving faster than their surrounding stars in a supervirial clustersuggests that the initial masses of forming stars may be related to theirinitial kinematic states. Additionally, a clockwise rotation preference isdetected. A weak sign of inverse mass segregation is also identified amongstars excluding the Trapezium stars, though it could be a sample bias. Finally,this study reports the discovery of four new candidate spectroscopic binarysystems.

The 3D Kinematics of the Orion Nebula Cluster II: Mass-dependent Kinematics of the Inner Cluster