The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a
  Bimodal Bulge?
  Radial velocities of 2768 fundamental mode RR Lyrae stars (RRLs) toward the
Southern Galactic bulge are presented, spanning the southern bulge from -8 < l
< +8 and -3 < b <-6. Distances derived from the pulsation properties of the
RRLs are combined with Gaia proper motions to give constraints on the orbital
motions of 1389 RRLs. The majority (~75%) of the bulge RRLs have orbits
consistent with these stars being permanently bound to <3.5 kpc from the
Galactic Center, similar to the bar. However, unlike the bulge giants, the RRLs
exhibit slower rotation and a higher velocity dispersion. The higher velocity
dispersion arises almost exclusively from halo interlopers passing through the
inner Galaxy. We present 82 stars with space velocities > 500 km/s and find
that the majority of these high-velocity stars are halo interlopers; it is
unclear if a sub-sample of these stars with similar space velocities have a
common origin. Once the 25% of the sample represented by halo interlopers is
cleaned, we can clearly discern two populations of bulge RRLs in the inner
Galaxy. One population of RRLs is not as tightly bound to the Galaxy (but is
still confined to the inner ~3.5 kpc), and is both spatially and kinematically
consistent with the barred bulge. The second population is more centrally
concentrated and does not trace the bar. One possible interpretation is that
this population was born prior to bar formation, as its spatial location,
kinematics and pulsation properties suggest, possibly from an accretion event
at high redshift.
