Environmental regulation of cloud and star formation in galactic bars
  The strong time-dependence of the dynamics of galactic bars yields a complex
and rapidly evolving distribution of dense gas and star forming regions.
Although bars mainly host regions void of any star formation activity, their
extremities can gather the physical conditions for the formation of molecular
complexes and mini-starbursts. Using a sub-parsec resolution hydrodynamical
simulation of a Milky Way-like galaxy, we probe these conditions to explore how
and where bar (hydro-)dynamics favours the formation or destruction of
molecular clouds and stars. The interplay between the kpc-scale dynamics (gas
flows, shear) and the parsec-scale (turbulence) is key to this problem. We find
a strong dichotomy between the leading and trailing sides of the bar, in term
of cloud fragmentation and in the age distribution of the young stars. After
orbiting along the bar edge, these young structures slow down at the
extremities of the bar, where orbital crowding increases the probability of
cloud-cloud collision. We find that such events increase the Mach number of the
cloud, leading to an enhanced star formation efficiency and finally the
formation of massive stellar associations, in a fashion similar to
galaxy-galaxy interactions. We highlight the role of bar dynamics in decoupling
young stars from the clouds in which they form, and discuss the implications on
the injection of feedback into the interstellar medium, in particular in the
context of galaxy formation.
