The Assembly History of M87 Through Radial Variations in Chemical
  Abundances of its Field Star And Globular Cluster Populations
  We present an extensive study of spectroscopically-derived chemical
abundances for M87 and its globular cluster (GC) system. Using observations
from the Mitchell spectrograph at McDonald, LRIS at Keck, and Hectospec on the
MMT, we derive new metallicity gradients from $\sim 2$ to $140$ kpc. We use a
novel hierarchical statistical framework to simultaneously separate the GC
system into subpopulations while measuring the metallicity gradients of those
subpopulations. We create physically-motivated spectral stacks of the GC
subpopulations by leveraging the output of this statistical framework to
perform the first application of abundance tagging in a massive ETG to better
constrain the origins of the GC subpopulations and, thus, the assembly history
of M87. We find a metal-poor, $\alpha$-enhanced population of GCs in both in
the inner and outer halo unanticipated by current cosmological simulations of
galaxy evolution. We use the remarkably flat metallicity gradients we find for
both the metal-rich and metal-poor GC subpopulations in the inner halo as
tentative evidence that some amount of the metal-poor GCs formed directly in
the halo of M87 at high redshift.
