12CO mapping of the low-metallicity BCD galaxy Mrk86

We have mapped the 12CO J=1-0 and J=2-1 line emission in Mrk86, one of the most metal-deficient Blue Compact Dwarf galaxies so far detected in 12CO. The 12CO emission is distributed in a horseshoe-like structure that follows the locus of the most recent star formation regions. The minimum in molecular-line emission corresponds to the position of an older, massive nuclear starburst. The H2 mass of the galaxy (in the range 0.4-5x10^7 Msun) and its morphology have been compared with the predictions of hydrodynamic simulations of the evolution of the interstellar medium surrounding a nuclear starburst. These simulations suggest that the physical conditions in the gas swept out by the starburst could have led to the formation of the ring of molecular gas reported here. This result provides an attractive scenario for explaining the propagation (in a galactic scale) of the star formation in dwarf galaxies.