Astron. Astrophys. 361, 877-887 (2000)

Compact star clusters of the LMC H II region N11 C ^*

Mohammad Heydari-Malayeri ¹, Pierre Royer ^{2  **}, Gregor Rauw ^2 ***, and Nolan R. Walborn <sup>3

1</sup> DEMIRM, Observatoire de Paris, 61 Avenue de l'Observatoire, 75014 Paris, France
² Université de Liège, Institut d'Astrophysique et de Géophysique, 5 Avenue de Cointe, 4000 Liège, Belgium
³ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

Received 4 April 2000 / Accepted 20 July 2000

Abstract

Based on imaging and spectroscopy obtained at the ESO NTT telescope and using an efficient image analysis algorithm, we study the core of the LMC OB association LH 13, particularly the two compact stellar clusters Sk-66^o41 and HNT in the H II region N 11C. We resolve Sk-66^o41 into 15 components and for the first time the HNT cluster into 70 stars, and derive photometry for the members. Moreover, from medium resolution spectroscopy we determine the spectral types for sixteen stars in N 11C. We compare the color-magnitude diagrams of the clusters with that of the field stars and discuss the cluster ages. With an age of 100 Myr, the HNT cluster appears significantly older than the very young ( Myr) Sk-66^o41 starburst. We suggest that most of the `field' O-stars in the core of N 11C have actually been ejected from Sk-66^o41 through dynamical interactions in the compact cluster. The properties of the Sk-66^o41 and HNT clusters suggest that we are viewing different star formation regions lying at different distances along the same line of sight.

Key words: stars: early-type ISM: H ii regions ISM: individual objects: N 11C galaxies: Magellanic Clouds

* Based on observations obtained at the European Southern Observatory, La Silla, Chile
** Research Fellow FNRS (Belgium)
*** Postdoctoral Researcher FNRS (Belgium)

Send offprint requests to: M. Heydari-Malayeri (Mohammad.Heydari-Malayeri@obspm.fr)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations and data reduction
  • 2.1. Imaging and deconvolution
  • 2.2. Spectroscopy with NTT/EMMI
• 3. Photometry results
  • 3.1. Components of the clusters
  • 3.2. Field stars
• 4. Spectral types
  • 4.1. Sk-66^o41 cluster
  • 4.2. HNT cluster
  • 4.3. Spectral types of the field stars
• 5. Color-magnitude diagrams
• 6. Discussion and concluding remarks
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000
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