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The diameters of the largest star-forming complexes in 67 Magellanic spiral and irregular galaxies and 16 Blue Compact Dwarf galaxies are found to scale with the luminosity of the galaxy to the 0.4 power. This is the same relation as for the largest complexes in bright spiral galaxies, found in our previous study. The total correlation now spans 11 magnitudes of absolute brightness and a factor of 70 in star complex size. These results are consistent with the interpretation that the largest complexes form by gravitational instabilities with a nearly constant product of gas velocity dispersion c and stability parameter Q, i.e., cQ = 5-10 km/s. BCD galaxies have complexes that are a factor of two larger for a given luminosity than Magellanic or spiral galaxies.
We also measured complex diameters at the ends of the bars in barred galaxies and compared these to the largest complexes elsewhere in the disk. The end-of-bar complexes in Magellanic irregular galaxies and in flat-barred spiral galaxies are 1.5-2 times larger than those elsewhere in the disk, but the end-of-bar complexes in exponential-barred spirals tend to be no larger than the others in the disk.
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