Understanding the velocity distribution of the Galactic Bulge with
  APOGEE and Gaia
  We revisit the stellar velocity distribution in the Galactic bulge/bar region
with APOGEE DR16 and {\it Gaia} DR2, focusing in particular on the possible
high-velocity (HV) peaks and their physical origin. We fit the velocity
distributions with two different models, namely with Gauss-Hermite polynomial
and Gaussian mixture model (GMM). The result of the fit using Gauss-Hermite
polynomials reveals a positive correlation between the mean velocity
($\bar{V}$) and the "skewness" ($h_{3}$) of the velocity distribution, possibly
caused by the Galactic bar. The $n=2$ GMM fitting reveals a symmetric
longitudinal trend of $|\mu_{2}|$ and $\sigma_{2}$ (the mean velocity and the
standard deviation of the secondary component), which is inconsistent to the
$x_{2}$ orbital family predictions. Cold secondary peaks could be seen at
$|l|\sim6^\circ$. However, with the additional tangential information from {\it
Gaia}, we find that the HV stars in the bulge show similar patterns in the
radial-tangential velocity distribution ($V_{\rm R}-V_{\rm T}$), regardless of
the existence of a distinct cold HV peak. The observed $V_{\rm R}-V_{\rm T}$
(or $V_{\rm GSR}-\mu_{l}$) distributions are consistent with the predictions of
a simple MW bar model. The chemical abundances and ages inferred from ASPCAP
and CANNON suggest that the HV stars in the bulge/bar are generally as old as,
if not older than, the other stars in the bulge/bar region.
