The contribution of brown dwarfs to the local mass budget of the Galaxy

Based on the recent discoveries of free floating brown dwarfs we derive estimates of the local mass density of this population of objects. Mass density estimates from various surveys span the range 0.03 to 0.005 M pc−3. These estimates are compared with the local mass densities of the other constituents of the galactic disk and, in particular, with the dynamically determined total local mass density. We argue that brown dwarfs might indeed contribute significantly to the local mass budget, but that a local mass density as high as 0.03 M pc−3 as suggested by Ruiz et al. (1997) is rather unlikely.