APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
  The SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE)
survey has obtained high-resolution spectra for thousands of red giant stars
distributed among the massive satellite galaxies of the Milky Way (MW): the
Large and Small Magellanic Clouds (LMC/SMC), the Sagittarius Dwarf (Sgr),
Fornax (Fnx), and the now fully disrupted \emph{Gaia} Sausage/Enceladus (GSE)
system. We present and analyze the APOGEE chemical abundance patterns of each
galaxy to draw robust conclusions about their star formation histories, by
quantifying the relative abundance trends of multiple elements (C, N, O, Mg,
Al, Si, Ca, Fe, Ni, and Ce), as well as by fitting chemical evolution models to
the [$\alpha$/Fe]-[Fe/H] abundance plane for each galaxy. Results show that the
chemical signatures of the starburst in the MCs observed by Nidever et al. in
the $\alpha$-element abundances extend to C+N, Al, and Ni, with the major burst
in the SMC occurring some 3-4 Gyr before the burst in the LMC. We find that Sgr
and Fnx also exhibit chemical abundance patterns suggestive of secondary star
formation epochs, but these events were weaker and earlier ($\sim$~5-7 Gyr ago)
than those observed in the MCs. There is no chemical evidence of a second
starburst in GSE, but this galaxy shows the strongest initial star formation as
compared to the other four galaxies. All dwarf galaxies had greater relative
contributions of AGB stars to their enrichment than the MW. Comparing and
contrasting these chemical patterns highlight the importance of galaxy
environment on its chemical evolution.
