From VVV Survey
Goal 10: To identify high proper motion objects and background QSOs
This last goal links the –seemingly unrelated– intrinsically faintest and brightest objects in the Universe. On the faint end we would use proper motions to find nearby late M-type stars, brown dwarfs (L and T types), and high-velocity halo stars. The proper motions will probably turn up some of the most interesting low-mass objects, and UKIDSS, DENIS and 2MASS will be used in some cases to extend the time baseline. On the intrinsically bright end, variability would also allow us to identify background quasars, providing an extragalactic reference scale for future proper motions . QSOs have a relatively broad colour range depending on their redshift, and their intrinsic variability increases monotonically with increasing time lags ; their amplitudes should be > 0.2 mag in the IR . We estimate that we will find > 500 AGN assuming a surface density of 2/deg2 with K < 15.5  in the regions above and below the disk where AK < 0.5 mag.