RSAA Colloquia / Seminars / Feast-of-Facts: Tuesday, 10 November 2015, 11:00-12:00; Duffield Lecture Theatre

Ortwin Gerhard

"The New Milky Way: Peanut Bulge and Long Bar"

Data from the VVV NIR survey of the inner Milky Way show that our Galaxy has a strongly peanut-shaped bulge. Extending the analysis to larger radii with other surveys shows that the long bar is aligned with the bulge and extends to about 30 degrees longitude. The outermost parts of the bar are dominated by a new superthin, presumably younger component. Dynamical models based on the 3D bulge density and the BRAVA kinematic data allow us to determine the mass in the bulge region and to put constraints on the mass-to-light ratio and dark matter content in the bulge as well as on the bar’s pattern speed. The Milky Way bulge appears to have been mostly formed from the disk through a bar and buckling instability, with little evidence for a ’classical’, merger-built bulge.