Abstract
The Galactic bulge and bar are critical to our understanding of the Milky
Way. However, due to the lack of reliable stellar distances, the structure and
kinematics of the bulge/bar beyond the Galactic center have remained largely
unexplored. Here, we present a method to measure distances of luminous red
giants using a period-amplitude-luminosity relation anchored to the Large
Magellanic Cloud, with random uncertainties of 10-15% and systematic errors
below 1-2%. We apply this method to data from the Optical Gravitational Lensing
Experiment (OGLE) to measure distances to $190,302$ stars in the Galactic bulge
and beyond out to 20 kpc. Using this sample we measure a distance to the
Galactic center of $R_0$ = $8108\pm106_{\rm stat}\pm93_{\rm sys}$ pc,
consistent with astrometric monitoring of stars orbiting Sgr A*. We cross-match
our distance catalog with Gaia DR3 and use the subset of $39,566$ overlapping
stars to provide the first constraints on the Milky Way's velocity field
($V_R,V_\phi,V_z$) beyond the Galactic center. We show that the $V_R$
quadrupole from the bar's near side is reflected with respect to the Galactic
center, indicating that the bar is both bi-symmetric and aligned with the inner
disk, and therefore dynamically settled along its full extent. We also find
that the vertical height $V_Z$ map has no major structure in the region of the
Galactic bulge, which is inconsistent with a current episode of bar buckling.
Finally, we demonstrate with N-body simulations that distance uncertainty plays
a major factor in the alignment of the major and kinematic axes of the bar and
distribution of velocities, necessitating caution when interpreting results for
distant stars.