Sebastien Lepine, American Museum of Natural History

"Probing the Galactic halo using cool subdwarfs"

The low-mass, cool subdwarfs (spectral type sdM) are the most
common denizens of the Galactic halo. They represent the end of the
main sequence for metal-poor (Pop. II) stars. Relatively large numbers
of them can be found in the immediate vicinity of the Sun (< 200 parsecs),
close enough for their proper motions to be accurately measured. This
makes them ideal probes of the kinematics (velocity-space distribution)
of Galactic halo stars. I will explain how nearby, halo subdwarfs can be
sifted from the bulk of local Galactic disk stars using catalogs of high
proper motion objects. I will also describe recent efforts to calibrate the
physical properties (mass, metallicity, multiplicity) of the cool
subdwarfs,
which remain poorly constrained by theoretical models.