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Our understanding of the brown dwarf population in star forming regions isdependent on knowing distances and proper motions, and therefore will beimproved through the Gaia space mission. In this paper, we select new samplesof very low mass objects (VLMOs) in Upper Scorpius using UKIDSS colors andoptimised proper motions calculated using Gaia DR1. The scatter in propermotions from VLMOs in Upper Scorpius is now (for the first time) dominated bythe kinematic spread of the region itself, not by the positional uncertainties.With age and mass estimates updated using Gaia parallaxes for early type starsin the same region, we determine masses for all VLMOs. Our final most completesample includes 453 VLMOs of which $\sim$125 are expected to be brown dwarfs.The cleanest sample is comprised of 131 VLMOs, with $\sim$105 brown dwarfs. Wealso compile a joint sample from the literature which includes 415 VLMOs, outof which 152 are likely brown dwarfs. The disc fraction among low-mass browndwarfs ($M<0.05 M_{\odot}$) is substantially higher than in more massiveobjects, indicating that discs around low-mass brown dwarfs survive longer thanin low-mass stars overall. The mass function for $0.01<M<0.1$ $M_{\odot}$ isconsistent with the Kroupa IMF. We investigate the possibility that some'proper motion outliers' have undergone a dynamical ejection early in theirevolution. Our analysis shows that the color-magnitude cuts used when selectingsamples introduce strong bias into the population statistics due to varyinglevel of contamination and completeness.

Very Low-Mass Stars and Brown Dwarfs in Upper Scorpius using Gaia DR1: Mass Function, Disks and Kinematics