Microlensing by Free-Floating Brown Dwarfs

We propose a near-infrared microlensing survey of the central 2 degree field of the Galactic Center, in an attempt to estimate the surface density and mass distribution of distant free-floating brown dwarfs in the bulge and in the disk, acting as lenses of bright stars towards the Galactic Center. We estimate the probability (optical depth) of microlensing events to be 10^-7 and the typical timescale (full-width) of the amplification lightcurve to be about 1 week. The necessary wide-field NIR survey technology should soon be available on UKIRT, CFHT, and with VISTA at ESO/Paranal.