The kinematics of star clusters, where most stars are born, provide valuable insights in the processes of their formation and evolution. The Orion Nebula Cluster (ONC), being the closest massive star cluster with active star formation is an ideal target for studying the history of star clusters. In this work, we analyze the kinematics of stars within 4 arcminute of the Trapezium, the heart of the ONC. Radial velocities and surface temperatures are retrieved from spectra acquired by the NIRSPEC instrument with adaptive optics (NIRSPAO) on the Keck II 10-m telescope. A three-dimensional kinematic map is then constructed by combining the proper motions previously measured by the Hubble Space Telescope (HST) ACS/WFPC2/WFC3IR. The measured root-mean-squared velocity dispersion in each direction is 2.27±0.08 km/s, higher than the virial equilibrium's requirement of 1.73 km/s, suggesting that the ONC core is supervirial. In addition, a negative correlation is detected between the relative velocity with respect to the neighbors of each star within a 0.1-pc radius and the interpolated stellar mass based on stellar evolutionary tracks. Such a relation is not present between the velocity dispersion and stellar mass, indicating that energy equipartition is not the cause for the negative correlation and has not yet occurred within the cluster. Low-mass stars moving faster than their surrounding stars in a supervirial cluster suggests that the initial masses of forming stars are related to their initial kinematic states. Furthermore, inverse mass segregation is detected among the sources excluding the most massive Trapezium stars. However, this finding may be subject to a bias in the sample. Lastly, a counter-clockwise rotation is identified in the region.
[Poster PDF File]