We present the kinematic results from our ARGOS spectroscopic survey of the Galactic bulge of the Milky Way .
Our aim is to understand the formation of the Galactic bulge .
We examine the kinematics of about 17,400 stars in the bulge located within 3.5 kpc of the Galactic centre , identified from the 28,000-star ARGOS survey .
We aim to determine if the formation of the bulge has been internally driven from disk instabilities as suggested by its boxy shape , or if mergers have played a significant role as expected from \Lambda CDM simulations .
From our velocity measurements across latitudes b = –5 ^ { \circ } , –7.5 ^ { \circ } and –10 ^ { \circ } we find the bulge to be a cylindrically rotating system that transitions smoothly out into the disk .
Within the bulge , we find a kinematically distinct metal-poor population ( [ Fe/H ] < -1.0 ) that is not rotating cylindrically .
The 5 \% of our stars with [ Fe/H ] < -1.0 are a slowly rotating spheroidal population , which we believe are stars of the metal-weak thick disk and halo which presently lie in the inner Galaxy .
The kinematics of the two bulge components that we identified in ARGOS paper III ( mean [ Fe/H ] \approx –0.25 and [ Fe/H ] \approx +0.15 , respectively ) demonstrate that they are likely to share a common formation origin and are distinct from the more metal-poor populations of the thick disk and halo which are co-located inside the bulge .
We do not exclude an underlying merger generated bulge component but our results favour bulge formation from instabilities in the early thin disk .