AbstractA proper motion study of a field of 20′ × 20′ inside Plaut's low extinction window (l,b)=(0o, −8o), has been completed. Relative proper motions and photographicBVphotometry have been derived for ~ 21,000 stars reaching toV~ 20.5 mag, based on the astrometric reduction of 43 photographic plates, spanning over 21 years of epoch difference. Proper motion errors are typically 1 mas yr−1. Cross-referencing with the 2MASS catalog yielded a sample of ~ 8700 stars, from which predominantly disk and bulge subsamples were selected photometrically from theJHcolor-magnitude diagram. The two samples exhibited different proper-motion distributions, with the disk displaying the expected reflex solar motion. Galactic rotation was also detected for stars between ~2 and ~3 kpc from us. The bulge sample, represented by red giants, has an intrinsic proper motion dispersion of (σl, σb) = (3.39, 2.91)±(0.11, 0.09) mas yr−1, which is in good agreement with previous results. A mean distance of$6.37^{+0.87}_{-0.77}$kpc has been estimated for the bulge sample, based on the observedKmagnitude of the horizontal branch red clump. The metallicity [M/H] distribution was also obtained for a subsample of 60 bulge giants stars, based on calibrated photometric indices. The observed [M/H] shows a peak value at [M/H] ~ −0.1 with an extended metal poor tail and around 30% of the stars with supersolar metallicity. No change in proper motion dispersion was observed as a function of [M/H]. We are currently in the process of obtaining CCDUBV RIphotometry for the entire proper-motion sample of ~ 21,000 stars.
A ground-based proper motion study of 12 nearby globular clusters