The OB Associations of 30 Doradus in the Large Magellanic Cloud. II. Stellar Content and Initial Mass Function

From photometric and spectroscopic observations of the stars in 30 Doradus we determine the effective stellar temperatures and bolometric magnitudes. We construct the theoretical H-R diagram, and using stellar evolution models we then bin the stars by mass to obtain the initial mass function (IMF). The IMF shows marked curvature; it flattens out at lower masses, even for those masses above which the photometry is complete. Best estimates of the IMF slope yield values of {GAMMA} - 1.5 +/- 0.2 for M >~ 12M_sun_, where the Salpeter slope is {GAMMA} = - 1.35. However, there are indications that different regions of 30 Doradus have different IMF slopes, perhaps as the result of sequential star formation effects.