Dating the tidal disruption of globular clusters with Gaia data on their
  stellar streams
  The Gaia mission promises to deliver precision astrometry at an unprecedented
level, heralding a new era for discerning the kinematic and spatial coordinates
of stars in our Galaxy. Here, we present a new technique for estimating the age
of tidally disrupted globular cluster streams using the proper motions and
parallaxes of tracer stars. We evolve the collisional dynamics of globular
clusters within the evolving potential of a Milky Way-like halo extracted from
a cosmological $\Lambda$CDM simulation and analyze the resultant streams as
they would be observed by Gaia. The simulations sample a variety of globular
cluster orbits, and account for stellar evolution and the gravitational
influence of the disk of the Milky Way. We show that a characteristic
timescale, obtained from the dispersion of the proper motions and parallaxes of
stars within the stream, is a good indicator for the time elapsed since the
stream has been freely expanding away due to the tidal disruption of the
globular cluster. This timescale, in turn, places a lower limit on the age of
the cluster. The age can be deduced from astrometry using a modest number of
stars, with the error on this estimate depending on the proximity of the stream
and the number of tracer stars used.
