Open Cluster Chemical Homogeneity Throughout the Milky Way
  The chemical homogeneity of surviving stellar clusters contains important
clues about interstellar medium (ISM) mixing efficiency, star formation, and
the enrichment history of the Galaxy. Existing measurements in a handful of
open clusters suggest homogeneity in several elements at the 0.03 dex level.
Here we present (i) a new cluster member catalog based only on APOGEE radial
velocities and Gaia-DR2 proper motions, (ii) improved abundance uncertainties
for APOGEE cluster members, and (iii) the dependence of cluster homogeneity on
Galactic and cluster properties, using abundances of eight elements from the
APOGEE survey for ten high-quality clusters. We find that cluster homogeneity
is uncorrelated with Galactocentric distance, |Z|, age, and metallicity.
However, velocity dispersion, which is a proxy for cluster mass, is positively
correlated with intrinsic scatter at relatively high levels of significance for
[Ca/Fe] and [Mg/Fe]. We also see a possible positive correlation at a low level
of significance for [Ni/Fe], [Si/Fe], [Al/Fe], and [Fe/H], while [Cr/Fe] and
[Mn/Fe] are uncorrelated. The elements that show a correlation with velocity
dispersion are those that are predominantly produced by core-collapse
supernovae (CCSNe). However, the small sample size and relatively low
correlation significance highlight the need for follow-up studies. If borne out
by future studies, these findings would suggest a quantitative difference
between the correlation lengths of elements produced predominantly by Type~Ia
SNe versus CCSNe, which would have implications for Galactic chemical evolution
models and the feasibility of chemical tagging.
