10 November 2008
Evan Kirby (Santa Cruz)
"Building the Milky Way Halo: An Inspection of the dSph Building Blocks"
I present new metallicity measurements for 298 individual red giant
branch stars in eight of the least luminous dwarf spheroidal galaxies
(dSphs) in the Milky Way (MW) system. My technique is based on medium
resolution Keck/DEIMOS spectroscopy coupled with spectral
synthesis. These data include the first spectroscopic metallicities at
[Fe/H] < -3.0 of stars in a dwarf galaxy, with individual stellar
metallicities as low as [Fe/H] = -3.3. I also demonstrate that the
luminosity-metallicity relation previously seen in more luminous dSph
galaxies (M_V = -13.4 to -8.8) extends smoothly down to an absolute
magnitude of M_V = -3.7. Comparing the metallicity distributions of
the dSphs to the oldest part of the MW, its stellar halo, can test the
hypothesis that the halo formed via the accretion of dSphs. For more
information, please visit http://arxiv.org/abs/0807.1925.