Astron. Astrophys. 347, 850-859 (1999)

Microlensing optical depth of the Large Magellanic Cloud

É. Aubourg ¹, N. Palanque-Delabrouille ¹, P. Salati ^2,3, M. Spiro ¹ and R. Taillet <sup>2,3

1</sup> CEA, DSM, DAPNIA, Centre d'Études de Saclay, F-91191 Gif-sur-Yvette Cedex, France
² LAPTH, chemin de Bellevue, B.P. 110, F-74941 Annecy-le-Vieux Cedex, France
³ Université de Savoie, B.P. 1104, F-73011 Chambéry Cedex, France

Received 27 January 1999 / Accepted 12 May 1999

Abstract

The observed microlensing events towards the LMC do not have yet a coherent explanation. If they are due to Galactic halo objects, the nature of these objects is puzzling - half the halo in dark objects. On the other hand, traditional models of the LMC predict a self-lensing optical depth about an order of magnitude too low, although characteristics of some of the observed events favor a self-lensing explanation. We present here two models of the LMC taking into account the correlation between the mass of the stars and their velocity dispersion: a thin Mestel disk, and an ellipsoidal model. Both yield optical depths, event rates, and event duration distributions compatible with the observations. The grounds for such models are discussed, as well as their observational consequences.

Key words: Galaxy: halo Galaxy: kinematics and dynamics Galaxy: stellar content cosmology: dark matter cosmology: gravitational lensing

Send offprint requests to: Nathalie.Delabrouille@cea.fr

SIMBAD Objects

Contents

• 1. Introduction
• 2. The Large Magellanic Cloud as a thin Mestel disk
  • 2.1. Description of the model
  • 2.2. Microlensing parameters
  • 2.3. Tidal effects
• 3. Ellipsoidal models
  • 3.1. Description of the model
  • 3.2. Microlensing parameters
• 4. Discussion and conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: June 6, 1999
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