Determining Photometric Metallicities of dSph Stellar Populations
  If there are so few upper red-giant branch stars in the SDSS-discovered dwarf
galaxies, how can we find the true population structure without extensive
spectroscopy?
  We review recent photometric and spectroscopic studies of the Ultra-Faint
Dwarf Galaxies, and determine a new method of estimating [Fe/H] with a
combination of Washington and Stromgren filters, using Bootes I dSph as an
example. We can use the CT1by filters alone to achieve 0.3 dex resolution in
[Fe/H], and 0.5 Gyr resolution in age. Both the Washington and Stromgren
filters, C and v, are sensitive to CN-variations; however, in stars with a
large deficiency of heavy elements the CN bands are weak and not important. The
[Fe/H]-sensitivity of the Washington and Stromgren combination is at least
twice as great as the SDSS filters, and this work maintains that resolution on
the lower red-giant branch, where other calibrations fail.
