The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of
  metal-poor stars in the Galactic bulge
  Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the
importance of a classical, pressure-supported component within the central part
of the Milky Way is still being debated. It should be most visible at low
metallicity, a regime that has not yet been studied in detail. Using
metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey
(PIGS) has collected a large sample of metal-poor ([Fe/H] < -1.0) stars in the
inner Galaxy to address this open question. We use PIGS to trace the metal-poor
inner Galaxy kinematics as function of metallicity for the first time. We find
that the rotational signal decreases with decreasing [Fe/H], until it becomes
negligible for the most metal-poor stars. Additionally, the velocity dispersion
increases with decreasing metallicity for -3.0 < [Fe/H] < -0.5, with a gradient
of -44 $\pm$ 4 km$\,$s$^{-1}\,$dex$^{-1}$. These observations may signal a
transition between Galactic components of different metallicities and
kinematics, a different mapping onto the boxy/peanut-shaped bulge for former
disk stars of different metallicities and/or the secular dynamical and
gravitational influence of the bar on the pressure-supported component. Our
results provide strong constraints on models that attempt to explain the
properties of the inner Galaxy.
