One of the most obvious global tests of mechanical feedback is to identify the parent stellar populations, or their remains, with the superbubbles. M31 (Brinks & Bajaja 1986) and M33 (Deul & den Hartog 1990) both show correlations of OB assocations with H i holes. However, Ho II shows contradictory results, based on the H i hole catalog compiled by Puche et al. (1992). Tongue & Westpfahl (1995) found that the SN rate implied by radio continuum emission is consistent with the hole energetics in that galaxy. However, Rhode et al. (1999) carried out a direct, BVR search for remnant stellar populations within the H i holes, and found little evidence for the expected stars. But Stewart et al. (2000) used far-UV data from the Ultraviolet Imaging Telescope and H images to conclude that a significant correlation between the H i holes and recent star formation does indeed support a feedback origin for the holes.
It is perhaps unsurprising that studies of Ho II yield these confusing results in view of that galaxy's distance of 3 Mpc. The LMC, which is 60 times closer, presents much better spatial resolution and should therefore yield less ambiguous results. Kim et al. (1999) examined the correspondence between their H i shell catalog, catalogued H ii regions (Davies et al. 1976), and H imaging. Not only do they find a correspondence, but they are also able to identify an evolutionary sequence with respect to the relative sizes, expansion velocities, and H emission. Further investigation of the Magellanic Clouds should confirm and reveal more quantitative details of the mechanical feedback process (Oey, Gerken, & Walterbos, in preparation).