Microlensing in dark matter haloes |
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Authors: | Janne Holopainen Chris Flynn Alexander Knebe Stuart P. Gill Brad K. Gibson |
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Affiliation: | Tuorla Observatory, Väisäläntie 20, Piikkiö, FIN-21500, Finland;Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany;Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA;Centre for Astrophysics, University of Central Lancashire, Preston PR1 2HE |
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Abstract: | Using eight dark matter haloes extracted from fully self-consistent cosmological N -body simulations, we perform microlensing experiments. A hypothetical observer is placed at a distance of 8.5 kpc from the centre of the halo measuring optical depths, event durations and event rates towards the direction of the Large Magellanic Cloud. We simulate 1600 microlensing experiments for each halo. Assuming that the whole halo consists of massive astronomical compact halo objects (MACHOs), f = 1.0 , and a single MACHO mass is m M= 1.0 M⊙ , the simulations yield mean values of τ= 4.7+5.0−2.2× 10−7 and Γ= 1.6+1.3−0.6× 10−6 events star−1 yr−1. We find that triaxiality and substructure can have major effects on the measured values so that τ and Γ values of up to three times the mean can be found. If we fit our values of τ and Γ to the MACHO collaboration observations, we find f = 0.23+0.15−0.13 and m M= 0.44+0.24−0.16 . Five out of the eight haloes under investigation produce f and m M values mainly concentrated within these bounds. |
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Keywords: | gravitational lensing methods: N-body simulations Galaxy: structure dark matter |
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