We present a catalog of high-precision proper motions in the Orion Nebula Cluster ( ONC ) , based on Treasury Program observations with the Hubble Space Telescope ’ s ( HST ) ACS/WFC camera .
Our catalog contains 2,454 objects in the magnitude range of 14.2 < m _ { F 775 W } < 24.7 , thus probing the stellar masses of the ONC from \sim 0.4 M _ { \sun } down to \sim 0.02 M _ { \sun } over an area of \sim 550 arcmin ^ { 2 } .
We provide a number of internal velocity dispersion estimates for the ONC that indicate a weak dependence on the stellar location and mass .
There is good agreement with the published velocity dispersion estimates , although nearly all of them ( including ours at \sigma _ { v,x } = 0.94 and \sigma _ { v,y } = 1.25 mas yr ^ { -1 } ) might be biased by the overlapping young stellar populations of Orion A .
We identified 4 new ONC candidate runaways based on HST and the Gaia DR 2 data , all with masses less than \sim 1 M _ { \sun } .
The total census of known candidate runaway sources is 10 – one of the largest samples ever found in any Milky Way open star cluster .
Surprisingly , none of them has the tangential velocity exceeding 20 km s ^ { -1 } .
If most of them indeed originated in the ONC , it may compel re-examination of dynamical processes in very young star clusters .
It appears that the mass function of the ONC is not significantly affected by the lost runaways .