Probable member stars of the gravitational theory-testing globular clusters AM 1, Pal 3 and Pal 14

Abstract

Some of the Galactic outer halo globular clusters are excellent tools to probe gravitational theories in the regime of weak accelerations (Baumgardt et al. 2005). The measurement of the line-of-sight velocity dispersion among stars in these clusters will differentiate between the validity of Newtonian dynamics (low velocity dispersion) and the possiblity of modified Newtonian dynamics (MOND) or dark matter dominated globular clusters (high velocity dispersion). In this paper, the properties of probable member stars of the three best-case gravitational theory-testing clusters AM 1, Pal 3 and Pal 14 are presented. The member selection is based on VLT photometry in Johnson BV. The positions of the stars were determined with an accuracy of the order <=0.2 arcsec, allowing their direct use for follow-up spectroscopy. The distance, reddening, age, and metallicities of the clusters were estimated from isochrone fitting. Furthermore, improved structural parameters, like central coordinates, ellipticit

11 pages, 10 figures, accepted for publication in Astronomy & Astrophysics