The Bulge Radial Velocity/Abundance Assay ( BRAVA ) has accomplished a survey of 10,000 red giants in the Southern Galactic bulge , approximately spanning -8 ^ { \circ } < l < +8 ^ { \circ } and -3 ^ { \circ } < b < -8 ^ { \circ } , a region within roughly 1 kpc from the nucleus .
We find that the Galactic bulge at b = -4 ^ { \circ } displays a clear departure from solid body rotation , and that the rotation field along the major axis at b = -6 ^ { \circ } and b = -8 ^ { \circ } is identical to that at lower latitude ; this is “ cylindrical ” rotation , a hallmark observed in edge-on bars .
Comparison of the BRAVA dataset with an N-body bar shows that > 90 \% of the bulge population is in the bar , leaving little room for a “ classical ” bulge component .
We also report on the first iron abundance and composition measurements in the outer bulge , at b = -8 ^ { \circ } .
The iron abundance in this field falls on the trend of a suspected gradient measured from high resolution spectroscopy of bulge clump stars .
Further , we find that the trends of [ \alpha / Fe ] vs [ Fe/H ] that characterize the bulge at lower latitude are present 1 kpc from the nucleus , consistent with a rapid ( < 1 Gyr ) timescale for the formation of the bulge , even near its boundary .
Although the dynamics of the bulge are consistent with those of a dynamically buckled N-body bar , the presence of an abundance gradient is not compatible with purely dynamical processes ; we propose that missing baryonic physics is needed .
We also report on the remarkable massive bulge globular cluster Terzan 5 , which has a bimodal abundance and composition distribution , and is proposed as the remnant of a population of primordial building block stellar systems that formed the bulge .
Terzan 5 is presently a unique case , and it is important to test whether the dissolution of systems similar to it populated the bulge .