We analyze the kinematics and spatial distribution of fundamental-mode 15,599 RR Lyrae ( RRL ) stars in the Galactic bulge by combining OGLE-IV photometric data and Gaia DR2 proper motions .
We show that the longitudinal proper motion and the line-of-sight velocity give similar results for the rotation in the Galactic central regions .
The angular velocity of bulge RRLs is found to be around 35 km s ^ { -1 } kpc ^ { -1 } , significantly smaller than that for the majority of bulge stars ( 50 - 60 km s ^ { -1 } kpc ^ { -1 } ) ; bulge RRLs have larger velocity dispersion ( 120 - 140 km s ^ { -1 } ) than younger stars .
The dependence of the kinematics of the bulge RRLs on their metallicities is shown by their rotation curves and spatial distributions .
Metal-poor RRLs ( [ Fe/H ] < -1 ) show a smaller bar angle than metal-rich ones .
We also find clues suggesting that RRLs in the bulge are not dominated by halo stars .
These results might explain some previous conflicting results over bulge RRLs and help understand the chemodynamical evolution of the Galactic bulge .