We have been exploring the phase space and metallicity distributions of stars in the North Galactic Pole field SA 57. The data are deep (B ~ 22.5) proper motions and photometry, combined with Mayall 4-m spectroscopy using the HYDRA multifiber system to brighter (B ~ 19.5) limits. Our early spectroscopic results confirmed the existence of a retrograde rotating, halo moving group in this field. We have since obtained many more spectra, and we find the halo stars in our survey to show a high degree of clumping in their U- V-W-[Fe/H] distributions. From our data we conclude that (1) the halo is not a dynamically relaxed system, (2) phase space substructure could account for differences in halo kinematics derived from surveys along different lines of sight, and (3) the halo field star population may be derived predominantly from the accretion of stellar agglomerations, most likely dwarf galaxies. The latter conclusion agrees with that of Preston et al. (1994) from their work on blue, metal-poor stars.
Formation of the Galactic Halo...Inside and Out
- Pub Date:
- April 1996