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Astron. Astrophys. 352, L69-L72 (1999)

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Letter to the Editor

Low-mass stars in the massive H II region NGC 3603 *

Deep NIR imaging with ANTU/ISAAC

B. Brandl 1, W. Brandner 2, F. Eisenhauer 3, A.F.J. Moffat 4, F. Palla 5 and H. Zinnecker 6

1 Cornell University, Department of Astronomy, 222 Space Sciences Building, Ithaca, NY 14853, USA (brandl@astrosun.tn.cornell.edu)
2 University of Hawaii, Institute for Astronomy, 2680 Woodlawn Dr., Honolulu, HI 96822, USA
3 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany
4 Université de Montréal, Département de physique, C.P. 6128, Succ. Centre-ville, Montréal, QC, H3C 3J7, Canada and Observatoire du mont Mégantic
5 Osservatorio Astrofisico di Arcetri, Largo E.Fermi 5, 50125 Firenze, Italy
6 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

Received 8 September 1999 / Accepted 11 October 1999


We have observed NGC 3603, the most massive visible H II region known in the Galaxy, with ANTU(VLT1)/ISAAC in the near-infrared (NIR) [FORMULA], H, and [FORMULA]-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 [FORMULA] 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 [FORMULA] Myr. The NIR luminosity functions show that the cluster is populated in low-mass stars at least down to [FORMULA]. Our observations clearly show that sub-solar mass stars do form in massive starbursts.

Key words: telescopes – stars: Hertzsprung – Russel (HR) and C-M diagrams – stars: pre-main sequence – ISM: H ii regions – galaxies: starburst

* Based on observations obtained at the European Southern Observatory, Paranal (ESO Proposal ID 63.I-0015)

Send offprint requests to: B. Brandl

© European Southern Observatory (ESO) 1999

Online publication: November 23, 1999