Proper motions for HST observations in three off-axis bulge fields

Abstract

Aims. This is the second in a series of papers that attempt to unveil the kinematic structure of the Galactic bulge through studying radial velocities and proper motions. We report here ~15 000 new proper motions for three low foreground-extinction off-axis fields of the Galactic bulge. Methods. Proper motions were derived from a combination of Hubble Space TelescopeWide Field Planetary Camera 2 (WFPC2) and Advanced Camera for Surveys (ACS) images taken 8 and 9 years apart, and they reach accuracies better than 0.9 mas yr-1 for more than ~10 000 objects with magnitudes F814W ≤ 24. Results. The proper motion distributions in these fields are similar to those of Galactic minor axis bulge fields.We observe the rotation of main sequence stars below the turn-off within the Galactic bulge, as in the minor axis fields. Conclusions. Our stellar proper motions measurements show a significant bulge rotation for fields as far from the Galactic plane as b ≈ -8°. © ESO 2014.