The Milky Way bar/bulge in proper motions: a 3D view from VIRAC & Gaia
  We have derived absolute proper motions of the entire Galactic bulge region
from VIRAC and Gaia. We present these as both integrated on-sky maps and, after
isolating standard candle red clump (RC) stars, as a function of distance using
RC magnitude as a proxy. These data provide a new global, 3-dimensional view of
the Milky Way barred bulge kinematics. We find a gradient in the mean
longitudinal proper motion, $<\mu_l^\star>$, between the different sides of the
bar, which is sensitive to the bar pattern speed. The split RC has distinct
proper motions and is colder than other stars at similar distance. The proper
motion correlation map has a quadrupole pattern in all magnitude slices showing
no evidence for a separate, more axisymmetric inner bulge component. The
line-of-sight integrated kinematic maps show a high central velocity dispersion
surrounded by a more asymmetric dispersion profile. $\sigma_{\mu_l} /
\sigma_{\mu_b}$ is smallest, $\sim1.1$, near the minor axis and reaches
$\sim1.4$ near the disc plane. The integrated $<\mu_b>$ pattern signals a
superposition of bar rotation and internal streaming motion, with the near part
shrinking in latitude and the far part expanding. To understand and interpret
these remarkable data, we compare to a made-to-measure barred dynamical model,
folding in the VIRAC selection function to construct mock maps. We find that
our model of the barred bulge, with a pattern speed of 37.5 $\mathrm{km \,
s^{-1} \, kpc^{-1}}$, is able to reproduce all observed features impressively
well. Dynamical models like this will be key to unlocking the full potential of
these data.
