LMC self-lensing from a new perspective

¹ Institut für Theoretische Physik der Universität Zürich, 8057 Zürich, Switzerland e-mail: novatic@physik.unizh.ch
² Dipartimento di Fisica “E. R. Caianiello”, Università di Salerno, 84081 Baronissi (SA), Italy
³ Istituto Nazionale di Fisica Nucleare, sez. Napoli, Italy
⁴ International Institute for Advanced Scientific Studies, Vietri sul Mare (SA), Italy

Received: 17 October 2003
Accepted: 6 July 2004

Abstract

We present a new analysis of the location of the observed microlensing events in the direction of the Large Magellanic Cloud (LMC). This is carried out starting from a recently drawn coherent picture of the geometrical structure and dynamics of the LMC disk and by considering different configurations for the LMC bar. In this framework it clearly emerges that the spatial distribution of the events observed so far shows a near-far asymmetry. This turns out to be compatible with the optical depth calculated for the LMC halo objects. Our main conclusion, supported by a statistical analysis of the outcome of an evaluation of the microlensing rate, is that self-lensing cannot account for all the observed events. Finally we propose a general inequality to calculate quickly an upper limit to the optical depth along a line of view through the LMC center.