Numerical simulations of bar formation in the Local Group
  More than 50 per cent of present-day massive disc galaxies show a rotating
stellar bar. Their formation and dynamics have been widely studied both
numerically and observationally. Although numerical simulations in the
$\Lambda$CDM cosmological framework predict the formation of such stellar
components, there seems to be a tension between theoretical and observational
results. Simulated bars are typically larger in size and have slower pattern
speed than observed ones. We study the formation and evolution of barred
galaxies, using two $\Lambda$CDM zoom-in hydrodynamical simulations of the
CLUES project that follow the evolution of a cosmological Local Group-like
volume. We found that our simulated bars, at $z = 0$, are both shorter and
faster rotators than previous ones found in other studies on cosmological
simulations alleviating the tension mentioned above. These bars match the short
tail-end of the observed bar length distribution. In agreement with previous
numerical works, we find that bars form in those systems where the disc
self-gravity is dominant over the dark matter halo, making them unstable
against bar formation. Our bars developed in the last 3-4 Gyr until they
achieve their current length and strength; as bars grow, their lengths increase
while their rotation speeds decrease. Despite this slowdown, at redshift $z =
0$ their rotation speeds and size match well the observational data.
