The Low-Mass Stars in Starburst Clusters

If star formation depends strongly on the global properties of the environment in which they form, the slope of the IMF as well as the upper and lower mass cut-offs would be expected to vary significantly between violent starbursts and more quiescent star forming regions. To test this hypothesis we observed the stellar content of the two closest massive star forming regions, 30 Doradus and NGC 3603 with HST/NICMOS and VLT/ISAAC. Our observations are the most sensitive observations made to date of dense starburst cores, allowing us to investigate its lowmass stellar population with unprecedented quality. The NIR luminosity function of 30 Doradus shows no evidence for a truncation down to at least 1M⊙, its stellar core R136 is populated in low-mass stars to at least 2M⊙ and NGC 3603, which is very similar to R136, down to 0.1M⊙. Our observations clearly show that low-mass stars do form in massive starbursts.