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S. Lépine (American Museum of Natural History)
SEGUE will investigate the local kinematic structure of the Galactic halo by obtaining complete velocity-space (UVW) data for a large number (\approx 10,000) of local (<500pc) halo subdwarfs. High proper motion stars with \mu > 0.04\arcsec yr-1 are selected from the AMNH all-sky proper motion survey, which is >99% complete down to V=19. The catalog has an object density of \approx40 stars per square degrees. Stars are placed on a reduced proper motion diagram, which plots the quantity V+5\log(\mu)+5 against V-J color. In this diagram, white dwarfs, giants, disk dwarfs, and halo subdwarfs all occupy very specific loci and can be separated. Halo subdwarfs (\approx8 stars per square degree) are selected as targets for SEGUE spectroscopy, from which radial velocities and metallicities are obtained. Photometric distances are estimated based on ugriz colors and metallicities. Proper motions and radial velocities are then used to calculate the motion vectors. The overall distribution will yield a signature of the global structure of the Galactic halo, from the point of view of its low-mass star constituents. The resulting, densely sampled, UVW velocity-space distribution will also be searched for signs of dynamical substructure in the halo (streamers, merger events, density waves).
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.