Characterizing the Heavy Elements in Globular Cluster M22 and an
  Empirical s-process Abundance Distribution Derived from the Two Stellar
  Groups
  We present an empirical s-process abundance distribution derived with
explicit knowledge of the r-process component in the low-metallicity globular
cluster M22. We have obtained high-resolution, high signal-to-noise spectra for
6 red giants in M22 using the MIKE spectrograph on the Magellan-Clay Telescope
at Las Campanas Observatory. In each star we derive abundances for 44 species
of 40 elements, including 24 elements heavier than zinc (Z=30) produced by
neutron-capture reactions. Previous studies determined that 3 of these stars
(the "r+s group") have an enhancement of s-process material relative to the
other 3 stars (the "r-only group"). We confirm that the r+s group is moderately
enriched in Pb relative to the r-only group. Both groups of stars were born
with the same amount of r-process material, but s-process material was also
present in the gas from which the r+s group formed. The s-process abundances
are inconsistent with predictions for AGB stars with M =< 3 Msun and suggest an
origin in more massive AGB stars capable of activating the Ne-22(alpha,n)Mg-25
reaction. We calculate the s-process "residual" by subtracting the r-process
pattern in the r-only group from the abundances in the r+s group. In contrast
to previous r- and s-process decompositions, this approach makes no assumptions
about the r- and s-process distributions in the solar system and provides a
unique opportunity to explore s-process yields in a metal-poor environment.
