We use high resolution numerical simulations in order to analyze the stellar
bar evolution in spinning dark matter (DM) halos. Previous works have shown
that the halo spin has a substantial effect on the bar evolution and can lead
to bar dissolution following the vertical buckling instability. Here, we invoke
the DM spin sequence, λ=0−0.09, and study the effect of DM density
along this λ-sequence by varying the compactness of DM halo. We find
that (1) varying the DM density has a profound effect on the stellar bar
evolution along the λ-sequence, namely, on its amplitude, pattern
speed, buckling time, etc.; (2) For λ≳0.04, the buckling
instability has been delayed progressively, and does not occur when the bar has
reached its maximal strength; (3) Instead, stellar bars remain near maximal
strength, and their amplitude plateau stage extends over ∼1−7 Gyr,
terminating with the buckling instability; (4) Although stellar bars remain
strong during the plateau, their pattern speed stays nearly constant. The
reason for this unusual behavior of stellar bars follows from the highly
reduced gravitational torques which they experience due to the DM bar being
aligned with the stellar bar. The performed orbital analysis shows that the
delayed buckling results from a slow evolution of stellar oscillations along
the bar major and vertical axes -- thus postponing the action of the vertical
2:1 resonance which pumps the rotational energy into vertical motions; (5)
Peanut/boxy shaped bulges form at the beginning of the plateau and grow with
time; (6) Strong stellar bars in spinning halos can avoid fast braking,
resolving the long standing discrepancy between observations and N-body
simulations. This behavior of stellar bars along the λ- and DM
density-sequences, reveals a wealth of stellar bar properties which require
additional study.Comment: 12 pages, 16 figures, submitted to MNRA