  The evolution of the Milky Way bulge and its relationship with the other
Galactic populations is still poorly understood. The bulge has been suggested
to be either a merger-driven classical bulge or the product of a dynamical
instability of the inner disk. To probe the star formation history, the initial
mass function and stellar nucleosynthesis of the bulge, we performed an
elemental abundance analysis of bulge red giant stars. We also completed an
identical study of local thin disk, thick disk and halo giants to establish the
chemical differences and similarities between the various populations.
High-resolution infrared spectra of 19 bulge giants and 49 comparison giants in
the solar neighborhood were acquired with Gemini/Phoenix. All stars have
similar stellar parameters but cover a broad range in metallicity. A standard
1D local thermodynamic equilibrium analysis yielded the abundances of C, N, O
and Fe. A homogeneous and differential analysis of the bulge, halo, thin disk
and thick disk stars ensured that systematic errors were minimized. We confirm
the well-established differences for [O/Fe] (at a given metallicity) between
the local thin and thick disks. For the elements investigated, we find no
chemical distinction between the bulge and the local thick disk, which is in
contrast to previous studies relying on literature values for disk dwarf stars
in the solar neighborhood. Our findings suggest that the bulge and local thick
disk experienced similar, but not necessarily shared, chemical evolution
histories. We argue that their formation timescales, star formation rates and
initial mass functions were similar.
