Witness of gas infall and outflow in the young starburst dwarf galaxy NGC5253

We present (CO)-C-12(2-1) observations towards the dwarf galaxy NGC5253 using the Sub-millimeter Array. The data shows that a large amount of molecular gas is located in the central similar to 200 pc starburst region, physically associated with two young super stellar clusters (SSCs). The molecular gas traced by (CO)-C-12(2-1) is elongated along the minor axis (dust lane) of the galaxy and its kinematics suggest that there is an inflow of molecular gas to the direction of the central SSCs, as is also observed in HI gas at a larger scale. Due to their correlation in spatial and velocity domains, the central SSCs were likely formed from molecular gas in the nucleus. We compare the (CO)-C-12(2-1) with available H-2 1-0 S(1) data, and show that while the relatively cold gas traced by (CO)-C-12(2-1) is distributed around the central starburst region but also along the dust lane, the warm gas traced by H-2 1-0 S(1) is associated with the central H II region and other star-forming regions. Interestingly, a cavity in the H-2 1-0 S(1) emission is found to be spatially correlated with a Ha shell. This H alpha shell may trace a bipolar outflow from the central SSCs and the H-2 1-0 S(1) gas, the gas shocked by the outflow encountering the surrounding quiescent gas. We calculate a molecular gas inflow rate of similar to 2M(circle dot)yr(-1), a star formation rate of 0.3-0.5M(circle dot) yr(-1), and an ionized gas outflow being emitted from the SSCs with a rate of (5-25) x 10(-3) f M-circle dot yr(-1), where f is a volume filling factor.