Tracing the assembly of the Milky Way's disk through abundance
  clustering
  A major goal in the field of galaxy formation is to understand the formation
of the Milky Way's disk. The first step toward doing this is to empirically
describe its present state. We use the new high-dimensional dataset of 19
abundances from 27,135 red clump APOGEE stars to examine the distribution of
clusters defined using abundances. We explore different dimensionality
reduction techniques and implement a non-parametric agglomerate hierarchical
clustering method. We see that groups defined using abundances are spatially
separated, as a function of age. Furthermore, the abundance groups represent
different distributions in the [Fe/H]-age plane. Ordering our clusters by age
reveals patterns suggestive of the sequence of chemical enrichment in the disk
over time. Our results indicate that a promising avenue to trace the details of
the disk's assembly is via a full interpretation of the empirical connections
we report.
