Massive star formation in NGC 6946

We present Hα measurements of the late-type spiral galaxy NGC 6946. Assuming an initial mass function, we use the Hα data to calculate the total star formation rate and efficiency of massive star formation as a function of galactocentric radius. We then attempt to determine the factors influencing these quantities by comparing them to the surface densities of H I and H2 and the degree of compression suffered by the gas in spiral density wave theory. The rate of star formation is very closely correlated with the first power of the surface density of H2, and somewhat less correlated with the degree of compression of the gas predicted by density wave theory. In contrast, the efficiency of massive star formation is roughly constant across the face of the galaxy. These results are consistent with results from previous studies of our own and other galaxies