Chemical Signatures of the First Supernovae in the Sculptor Dwarf
  Spheroidal Galaxy
  We present a homogeneous chemical abundance analysis of five of the most
metal-poor stars in the Sculptor dwarf spheroidal galaxy. We analyze new and
archival high resolution spectroscopy from Magellan/MIKE and VLT/UVES and
determine stellar parameters and abundances in a consistent way for each star.
Two of the stars in our sample, at [Fe/H] = -3.5 and [Fe/H] = -3.8, are new
discoveries from our Ca K survey of Sculptor, while the other three were known
in the literature. We confirm that Scl 07-50 is the lowest metallicity star
identified in an external galaxy, at [Fe/H] = -4.1. The two most metal-poor
stars both have very unusual abundance patterns, with striking deficiencies of
the alpha elements, while the other three stars resemble typical extremely
metal-poor Milky Way halo stars. We show that the star-to-star scatter for
several elements in Sculptor is larger than that for halo stars in the same
metallicity range. This scatter and the uncommon abundance patterns of the
lowest metallicity stars indicate that the oldest surviving Sculptor stars were
enriched by a small number of earlier supernovae, perhaps weighted toward
high-mass progenitors from the first generation of stars the galaxy formed.
