Peanut bulge formation

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Time evolution of the surface density of a stellar disk seen edgeon in model RHG097. The disk forms a strong peanut bulge via buckling instability of the bar. During this instability (look at t=3.4 - 4.0 billion years map), the density of stars show signs of asymmetry about the disk midplane (z=0) -- clear sign of vertical oscillation of the whole bar. Once the bar is out of the instability, the disk settles down with a symmetric (about z=0 plane) peanut bulge. For details, click Saha, Pfenniger and Taam 2013

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