Shadows and photoevaporated flows from neutral clumps exposed to two ionizing sources

Neutral clumps immersed in H II regions are frequently found in star formation regions. We investigate here the formation of tails of neutral gas, which are not reached by the direct ionizing ux coming from two massive stars, using both an analytical approximation that allows us to estimate the shadow geometry behind the clumps for dieren t initial geometric congurations, and three-dimensional numerical simulations. We nd a good agreement between both approaches to this theoretically interesting problem. A particularly important application could be the proplyds that are found in the Trapezium cluster in Orion, which are being photoevaporated primordially by the O stars 1 Ori C and 2 Ori A.