We present optical/near-IR integral field unit ( IFU ) observations of a gas pillar in the Galactic H ii region NGC 6357 containing the young open star cluster Pismis 24 .
These observations have allowed us to examined in detail the gas conditions of the strong wind-clump interactions taking place on its surface .

By accurately decomposing the H \alpha line profile , we identify the presence of a narrow ( \sim 20 km s ^ { -1 } ) and broad ( 50–150 km s ^ { -1 } ) component , both of which we can associate with the pillar and its surroundings .
Furthermore , the broadest broad component widths are found in a region that follows the shape of the eastern pillar edge .
These connections have allowed us to firmly associate the broad component with emission from ionized gas within turbulent mixing layers on the pillar ’ s surface set up by the shear flows of the winds from the O stars in the cluster .
We discuss the implications of our findings in terms of the broad emission line component that is increasingly found in extragalactic starburst environments .
Although the broad line widths found here are narrower , we conclude that the mechanisms producing both must be the same .
The difference in line widths may result from the lower total mechanical wind energy produced by the O stars in Pismis 24 compared to that from a typical young massive star cluster found in a starburst galaxy .

The pillar ’ s edge is also clearly defined by dense ( \lesssim 5000 cm ^ { -3 } ) , hot ( \gtrsim 20 000 K ) , and excited ( via the [ N ii ] /H \alpha and [ S ii ] /H \alpha ratios ) gas conditions , implying the presence of a D-type ionization front propagating into the pillar surface .
Although there must be both photoevaporation outflows produced by the ionization front , and mass-loss through mechanical ablation , we see no evidence for any significant bulk gas motions on or around the pillar .
We postulate that the evaporated/ablated gas must be rapidly heated before being entrained .