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

We have observed NGC 3603, the most massive visible HII region known in the Galaxy, with ANTU(VLT1)/ISAAC in the near-infrared (NIR) J_s, H, and K_s 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.