Low-mass stars in the massive HII region NGC 3603 - Deep NIR imaging with ANTU/ISAAC

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We have observed NGC 3603, the most massive visible HII region known in the Galaxy, with ANTU(VLT1)/ISAAC in the near-infrared (NIR) Jₛ, H, and Kₛ bands. Our observations are the most sensitive observations made to date of this dense starburst region, allowing us to investigate with unprecedented quality its low-mass stellar population. Our mass limit to stars detected in all three bands is 0.1 Mo for a pre-main sequence star of age 0.7 Myr. The overall age of the pre-main sequence stars in the core region of NGC 3603 has been derived from isochrone fitting in the colour-magnitude diagram, leading to 0.3 - 1.0 Myr. The NIR luminosity functions show that the cluster is populated in low-mass stars at least down to 0.1 Mo. Our observations clearly show that sub-solar mass stars do form in massive starbursts.