Spinning dark matter haloes promote bar formation

Stellar bars are the most common non-axisymmetric structures in galaxies and their impact on the evolution of disc galaxies at all cosmological times can be significant. Classical theory predicts that stellar discs are stabilized against bar formation if embedded in massive spheroidal dark matter haloes. However, dark matter haloes have been shown to facilitate the growth of bars through resonant gravitational interaction. Still, it remains unclear why some galaxies are barred and some are not. In this study, we demonstrate that corotating (i.e. in the same sense as the disc rotating) dark matter haloes with spin parameters in the range of 0 < lambda(dm) < 0.07 - which are a definite prediction of modern cosmological models - promote the formation of bars and boxy bulges and therefore can play an important role in the formation of pseudo-bulges in a kinematically hot dark-matter-dominated disc galaxies. We find continuous trends for models with higher halo spins: bars form more rapidly, the forming slow bars are stronger and the final bars are longer. After 2 Gyr of evolution, the amplitude of the bar mode in a model with lambda(dm) = 0.05 is a factor of similar to 6 times higher, A(2)/A(0) = 0.23, than in the non-rotating halo model. After 5 Gyr, the bar is similar to 2.5 times longer. The origin of this trend is that more rapidly spinning (corotating) haloes provide a larger fraction of trailing dark matter particles that lag behind the disc bar and help growing the bar by taking away its angular momentum by resonant interactions. A counter-rotating halo suppresses the formation of a bar in our models. We discuss potential consequences for forming galaxies at high-redshift and present-day low-mass galaxies which have converted only a small fraction of their baryons into stars.