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Issue A&A Volume 395, Number 1, November III 2002 Page(s) 31 - 35 Section Galactic structure and dynamics DOI 10.1051/0004-6361:20021298

A&A 395, 31-35 (2002)
DOI: 10.1051/0004-6361:20021298

Are there MACHOs in the Milky Way halo?

A. M. Green^{1, 2} and K. Jedamzik<sup>3, 4

1</sup>  Department of Physics, Stockholm University, 106 91 Stockholm, Sweden (Present address.)
    e-mail: amg@physto.se
²  Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
³  Laboratoire de Physique Mathématique et Théorique, Université de Montpellier II, 34095 Montpellier Cedex 5, France (Present address.)
    e-mail: jedamzik@lpm.univ-montp2.fr
⁴  Max-Planck-Institut für Astrophysik, 85740 Garching, Germany

(Received 12 June 2002 / Accepted 5 September 2002)

Abstract
Microlensing searches aim to detect compact halo dark matter via its gravitational lensing effect on stars within the Large Magellanic Cloud. These searches have led to the claim that roughly one fifth of the galactic halo dark matter may be in the form of compact, solar-mass objects. We analyze this hypothesis by considering the goodness-of-fit of the best-fit halo dark matter solutions to the observational data. We show that the distribution of the durations of the observed microlensing events is significantly narrower than that expected to result from a standard halo lens population at 90 to 95% confidence, casting doubt on the lenses constituting halo dark matter. This conclusion may possibly be avoided if (i) the Milky Way halo is sufficiently nonstandard or (ii) a large fraction of the events are due to non-halo populations with event durations coincidentally close to those of the putative halo population or (iii) individual event durations have been seriously underestimated due to blending.

Key words: Galaxy: halo -- cosmology: dark matter

Offprint request: A. M. Green, amg@physto.se

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