ADS Astronomy Abstract Service

Title:
Absolute Proper Motions to B approximately 22.5: Large-Scale Streaming Motions and the Structure and Origin of the Galactic Halo
Authors:
MAJEWSKI, STEVEN R.; MUNN, JEFFREY A.; HAWLEY, SUZANNE L.
Journal:
Astrophysical Journal Letters v.459, p.L73
Publication Date:
03/1996
Origin:
APJ
ApJ Keywords:
GALAXY: KINEMATICS AND DYNAMICS, GALAXY: STRUCTURE, GALAXY: FORMATION, GALAXY: EVOLUTION, GALAXY: HALO, STARS: KINEMATICS
Abstract Copyright:
(c) 1996: The American Astronomical Society
Bibliographic Code:
1996ApJ...459L..73M

Abstract

With an enlarged sample of radial velocities, we explore the phase-space and metallicity distributions for a sample of dwarf stars with distances up to 8 kpc in a deep north Galactic pole proper motion survey. We find that the halo stars in the sample are concentrated into clumps in the combined phase-space and metallicity distribution, one of the most prominent clumps representing a retrograde, predominantly metal-poor ([Fe/H] < -0.8) stream moving toward the Galactic plane. These new data reveal that (1) the halo is not dynamically mixed but presently contains a significant fraction of stars with membership in correlated stellar streams, (2) phase-space substructure might account for differences in halo kinematics derived among surveys along different lines of sight, and (3) a significant fraction of the halo field star population may be derived from the accretion of stellar agglomerations (e.g., star clusters, satellite galaxies, or Searle & Zinn "fragments").