The orbital motion of the Arches cluster: clues on cluster formation near the Galactic Center

We have measured the proper motion of the Arches cluster near the Galactic Center (GC) with respect to the ambient field, using Keck/NIRC2 LGS-AO and VLT/NAOS-CONICA NGS-AO observations spanning a baseline of 4.3 yr. Combined with the radial velocity, we derive a 3D space motion of 232±30 km s‑1 for the Arches cluster. This motion is exceptionally large compared to molecular cloud orbits at the GC, and places stringent constraints on the formation scenarios for starburst clusters in dense, nuclear environments