APOGEE Chemical Abundances of the Sagittarius Dwarf Galaxy
  The Apache Point Observatory Galactic Evolution Experiment (APOGEE) provides
the opportunity to measure elemental abundances for C, N, O, Na, Mg, Al, Si, P,
K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze the
chemical abundance patterns of these elements for 158 red giant stars belonging
to the Sagittarius dwarf galaxy (Sgr). This is the largest sample of Sgr stars
with detailed chemical abundances and the first time C, N, P, K, V, Cr, Co, and
Ni have been studied at high-resolution in this galaxy. We find that the Sgr
stars with [Fe/H] $\gtrsim$ -0.8 are deficient in all elemental abundance
ratios (expressed as [X/Fe]) relative to the Milky Way, suggesting that Sgr
stars observed today were formed from gas that was less enriched by Type II SNe
than stars formed in the Milky Way. By examining the relative deficiencies of
the hydrostatic (O, Na, Mg, and Al) and explosive (Si, P, K, and Mn) elements,
our analysis supports the argument that previous generations of Sgr stars were
formed with a top-light IMF, one lacking the most massive stars that would
normally pollute the ISM with the hydrostatic elements. We use a simple
chemical evolution model, flexCE to further backup our claim and conclude that
recent stellar generations of Fornax and the LMC could also have formed
according to a top-light IMF.
