Interactions of high velocity clouds with the disk of the LMC

High-resolution (similar to 1.0'...2.4') IRAS maps, optical broad-band, and narrow-band images as well as H I lambda 21 cm data have been used in order to analyse the environment of two large-scale distortions (LMC 4 and DEM 268) in the disk of the Large Magellanic Cloud, This study has revealed cone-like structures connected to DEM 268 and LMC 4 indicating high-velocity cloud impacts as the most probable source of the formation of these two distortions. In both cases, the tip of the cone, which is a place of increased star formation, has a shape which is typical of supersonic motion of gaseous matter through a compressible medium. Expansion velocities of the cone-like structures of about 12 km . s(-1) can be derived from the H I lambda 21 cm data. From these velocities, ages of the distortions of about 40 Myr (LMC 4) and 36 Myr (DEM 268) are estimated. The energy input for the formation of the distortions might have been provided by high velocity clouds with masses of the order of 10(5) M(.) (assuming an initial velocity of 100 km . s(-1) relative to the disk of the LMC).