Nucleosynthesis and the Inhomogeneous Chemical Evolution of the Carina
  Dwarf Galaxy
  The detailed abundances of 23 elements in nine bright RGB stars in the Carina
dSph are presented based on high resolution spectra gathered at the VLT and
Magellan telescopes. A spherical model atmospheres analysis is applied using
standard methods to spectra ranging from 380 to 680 nm. The stars in this
analysis range from -2.9 < [Fe/H] < -1.3, and adopting the ages determined by
Lemasle et al. (2012), we are able to examine the chemical evolution of
Carina's old and intermediate-aged populations. One of the main results from
this work is the evidence for inhomogeneous mixing in Carina; a large
dispersion in [Mg/Fe] indicates poor mixing in the old population, an offset in
the [alpha/Fe] ratios between the old and intermediate-aged populations (when
examined with previously published results) suggests that the second star
formation event occurred in alpha-enriched gas, and one star, Car-612, seems to
have formed in a pocket enhanced in SN Ia/II products. This latter star
provides the first direct link between the formation of stars with enhanced SN
Ia/II ratios in dwarf galaxies to those found in the outer Galactic halo (Ivans
et al. 2003). Another important result is the potential evidence for SN II
driven winds. We show that the very metal-poor stars in Carina have not been
enhanced in AGB or SN Ia products, and therefore their very low ratios of
[Sr/Ba] suggests the loss of contributions from the early SNe II. Low ratios of
[Na/Fe], [Mn/Fe], and [Cr/Fe] in two of these stars support this scenario, with
additional evidence from the low [Zn/Fe] upper limit for one star. It is
interesting that the chemistry of the metal-poor stars in Carina is not similar
to those in the Galaxy, most of the other dSphs, or the UFDs, and suggests that
Carina may be at the critical mass where some chemical enrichment events are
lost through SN II driven winds.
