EDP Sciences
Free access
Volume 496, Number 2, March III 2009
Page(s) 465 - 468
Section Galactic structure, stellar clusters, and populations
DOI http://dx.doi.org/10.1051/0004-6361/200809968
Published online 09 February 2009
A&A 496, 465-468 (2009)
DOI: 10.1051/0004-6361/200809968

Research Note

Microlensing towards the LMC revisited by adopting a non-Gaussian velocity distribution for the sources

L. Mancini1, 2

1  Dipartimento di Fisica “E.R. Caianiello”, Universit di Salerno, via S. Allende, Baronissi (SA), Italy
    e-mail: lmancini@physics.unisa.it
2  Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy

Received 14 April 2008 / Accepted 8 December 2008

Aims. We discuss whether the Gaussian is a reasonable approximation of the velocity distribution of stellar systems that are not spherically distributed.
Methods. By using a non-Gaussian velocity distribution to describe the sources in the Large Magellanic Cloud (LMC), we reinvestigate the expected microlensing parameters of a lens population isotropically distributed either in the Milky Way halo or in the LMC (self lensing). We compare our estimates with the experimental results of the MACHO collaboration.
Results. An interesting result that emerges from our analysis is that, moving from the Gaussian to the non-Gaussian case, we do not observe any change in the form of the distribution curves describing the rate of microlensing events for lenses in the Galactic halo. The corresponding expected timescales and number of expected events also do not vary. Conversely, with respect to the self-lensing case, we observe a moderate increase in the rate and number of expected events. We conclude that the error in the estimate of the most likely value for the MACHO mass and the Galactic halo fraction in form of MACHOs, calculated with a Gaussian velocity distribution for the LMC sources, is not higher than 2%.

Key words: gravitational lensing -- Galaxy: halo -- galaxies: magellanic clouds -- galaxies: kinematics and dynamics -- cosmology: dark matter

© ESO 2009