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The Subaru Seminar is
usually held in Room 104 of the Hilo Base Facility, adjacent
to the main lobby. Everyone is welcome to attend. If you are
interested in giving a seminar, please contact Subaru
seminar organizers (Tomonori Usuda, Kumiko S. Usuda, Masahiko Hayashi, Masayuki Akiyama)
by email.
January 31, Monday at 11:00am
" Chemical Evolution of the Galaxy's Thick Disk and Outer Disk"
Bruce W. Carney (University of North Carolina)
Evidence will be reviewed regarding the age of the
Galaxy's thick disk, and new observations of the
behavior of metallicity vs. kinematics, and elemental
abundances relative to iron for a sample of thin disk
and thick disk stars will be presented. In combination
with other larger surveys, it appears that the thick disk
has experienced a very different chemical evolution than
the thin disk, and that it may well have arisen from an
independent galaxy's merger with the Milky Way. There are
even signs of an enhanced star formation rate in the old
thin disk following the merger. An exploration of
elemental abundance patterns of the outer Galactic disk
will also be explored. It appears that, contrary to
model expectations, the radial metallicity gradient
in the outer disk disappears beyond a Galactocentric distance
of about 12 kpc. The light elements Mg, Si, Ca, and Ti,
and the heavy element Eu, are enhanced relative to iron,
suggesting dominance of Type II supernovae and a vigorous
star formation rate, which also suggests mergers of
low-metallicity material has contributed to the growth
of the Galactic disk.