This is a multi-pronged collaborative investigation of stellar open clusters. The goal is to provide useful clues and constraints on a variety of astrophysical problems such as: (1) the shape of the Initial Mass Function and its universality or lack thereof; (2) the extent of convective overshoot in stellar cores; and (3) the metallicity gradient in the Galaxy. The project will also result in a database of high quality astrometric, photometric and spectroscopic data for a carefully chosen sample of open clusters.
This grant supports the astrometry portion of this investigation. Positional information, proper motions and cluster membership determinations will be acquired for 8 key open clusters to at least 6 apparent magnitudes (~250x) fainter than previous surveys, while maintaining current limits of proper motion accuracy (~0.005 "/yr). The collaborating team will conduct the photometry portion of this investigation. It will yield UBVRI apparent magnitudes and color indices for cluster members to ~1% internal precision for all stars in the astrometric database, as well as fainter stars in these 8 clusters and 6 additional clusters. From this data, a 'present day mass function' will be determined for a wide range of cluster ages, richness, galactic position and metallicity.
