Abstract
For some time the Milky Way has been understood as a barred disk galaxy. Star count observations have provided evidence for two bars at apparently different orientations, the boxy bulge and a long planar bar. We report recent work in which we argued for a scenario where these observations can be reproduced with a single boxy bulge/bar: an evolved bar from the stellar disk and the corresponding boxy bulge generated from it through secular evolution and buckling instability. We calculated the star count distributions along different lines-of-sight for a simulated barred galaxy and an observer at the Sun position, and compared them with observations of red clump magnitude distributions. We found a good agreement between the model and the observations, even though the simulation has a single boxy bulge/bar. In this model, the different apparent orientations of the boxy bulge and planar bar are partially due to the volume effect and partially to the leading ends of the bar.
Highlights
During the last four decades it has become clear that our Galaxy is a barred system
We report recent work in which we argued for a scenario where these observations can be reproduced with a single boxy bulge/bar: an evolved bar from the stellar disk and the corresponding boxy bulge generated from it through secular evolution and buckling instability
We found a good agreement between the model and the observations, even though the simulation has a single boxy bulge/bar
Summary
During the last four decades it has become clear that our Galaxy is a barred system (see ref. [1]). The two structures were detected at different longitudes: |l| < 12◦, and generally above the plane for the boxy bulge; and l between 20◦ and 30◦ for the flat long bar. These results are puzzling since such misaligned structures would be dynamically quite unstable. In [10], we tested quantitatively that such a model predicts magnitude-dependent star count observations in approximate agreement with observations For further tests some extra velocity predictions for general fields near the bar end are given
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