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Formation and evolution of galactic bulges

Spin up of classical bulges

A number of observations suggest that classical bulges rotate faster than the low lumonisity ellipticals but slower than boxy/peanut bulge which forms as result of buckling instability of a bar. Howerver, the origin of angular momentum in the classcial bulges remain known. In Saha, Martinez-Valpuesta and Gerhard (2012), we have shown that a low-mass initially non-rotating classical bulge can actually gain significant amount of angular momentum and spin up thereby. During the evolution, not only the classical bulge starts rotating but it rotates like a cylindrical rotator. This has an important implication for the Milky Way's bulge.

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