Program: GN-2009A-Q-29

In 2005 and 2007 we obtained NIRI/Altair images in the core of the globular star cluster M71. The 1.8 year baseline allowed us to determine proper motions for the stars in our field. We discovered that we had RESOLVED the internal proper motion dispersion in the cluster allowing us to derive a GEOMETRIC DISTANCE by comparing its radial velocity dispersion with its proper motion one. This derivation requires either that the stars used for radial velocities are the same as those with proper motions or that (uncertain) corrections are made. At the moment we are forced to make these corrections. In this proposal we plan on two key observations: 1) observe with GMOS-IFU in the core to obtain the velocity dispersion of the SAME stars that we are using for proper motions and 2) obtain a third imaging epoch to improve the proper motions and explore the internal cluster dynamics.