Kinematics of RR Lyrae stars in the Galactic bulge with OGLE-IV and Gaia DR2

Abstract

We analyze the kinematics and spatial distribution of 15,599 fundamental-mode RR Lyrae (RRL) stars in the Milky Way bulge by combining OGLE-IV photometric data and Gaia DR2 proper motions. We show that the longitudinal proper motions and the line-of-sight velocities can 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.

arXiv comment15 pages, 15 figures. Published by MNRAS

References in corpus (63)

• The Gaia mission
• Gaia Data Release 2: The astrometric solution
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Morphology, photometry and kinematics of N-body bars. I Three models with different halo central concentrations
• Gaia Data Release 2: Mapping the Milky Way disc kinematics
• Mapping the Three-Dimensional Density of the Galactic Bulge with VVV Red Clump Stars
• The Circular Velocity Curve of the Milky Way from $5$ to $25$ kpc
• Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation
• The photometric structure of the inner Galaxy
• ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way
• The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration
• Spiral arms, bar shape and bulge microlensing in the Milky Way
• The Bulge Radial Velocity Assay (BRAVA): II. Complete Sample and Data Release
• Modelling the Galactic Bar Using Red Clump Giants
• On a new theoretical framework for RR Lyrae stars I: the metallicity dependence
• Chemodynamical history of the Galactic Bulge
• ARGOS IV: The Kinematics of the Milky Way Bulge
• Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Bulge studies
• Deciphering the 3D structure of the old Galactic bulge from the OGLE RR Lyrae stars
• Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
• Modelling the Galactic bar using OGLE-II Red Clump Giant Stars
• The GIRAFFE Inner Bulge Survey (GIBS) III. Metallicity distributions and kinematics of 26 Galactic bulge fields
• The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge
• VVV Survey Near-Infrared Photometry of Known Bulge RR Lyrae stars: the Distance to the Galactic Center and Absence of a Barred Distribution of the Metal-Poor Population
• ARGOS II: The Galactic Bulge Survey
• The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations
• Reddening and metallicity maps of the Milky Way Bulge from VVV and 2MASS. I.The method and minor axis maps
• A New Photometric Model of the Galactic Bar using Red Clump Giants
• The Bulge Radial Velocity Assay (BRAVA): I. Sample Selection and a Rotation Curve
• Forming disk galaxies in wet major mergers. I. Three fiducial examples
• The Gravitational Force Field of the Galaxy Measured From the Kinematics of RR Lyrae in Gaia
• Before the Bar: Kinematic Detection of A Spheroidal Metal-Poor Bulge Component
• A boxy bulge in the Milky Way. Inversion of the stellar statistics equation with 2MASS data
• The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge
• The Optical Gravitational Lensing Experiment: Analysis of the bulge RR Lyrae population from the OGLE-III data
• APOGEE Kinematics I: Overview of the Kinematics of the Galactic Bulge as Mapped by APOGEE
• Fourier Dissection of Early-Type Galaxy Bars
• A parametric description of the 3D structure of the Galactic Bar/Bulge using the VVV survey
• The Vertical X-shaped Structure in the Milky Way: Evidence from a Simple Boxy Bulge Model
• The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a Bimodal Bulge?
• Variable stars in the VVV globular clusters. I. 2MASS-GC02 and Terzan10
• Metallicity-dependendent kinematics and morphology of the Milky Way bulge
• Age Demographics of the Milky Way Disk and Bulge
• Mapping the outer bulge with RRab stars from the VVV Survey
• The Galactic Thick Disc density profile traced with RR Lyrae stars
• Transverse kinematics of the Galactic bar-bulge from VVV and Gaia
• A machine learned classifier for RR Lyrae in the VVV survey
• The Stellar Halo in the Inner Milky Way: Predicted Shape and Kinematics
• The VVV Survey RR Lyrae Population in the Galactic Centre Region
• Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane
• Kinematics in the Galactic Bulge with APOGEE: II. High-Order Kinematical Moments and Comparison to Extragalactic Bar Diagnostics
• On the optimal calibration of VVV photometry
• A Near-infrared RR Lyrae census along the southern Galactic plane: the Milky Way's stellar fossil brought to light
• Into the Darkness: Classical and Type II Cepheids in the Zona Galactica Incognita
• Chemically-dissected rotation curves of the Galactic Bulge from Main Sequence proper motions
• Kinematics of the X-shaped Milky Way Bulge: Expectations from a Self-consistent N-body Model
• Forming disc galaxies in major mergers: III. The effect of angular momentum on the radial density profiles of disc galaxies
• Over 78 000 RR Lyrae Stars in the Galactic Bulge and Disk from the OGLE Survey
• Mapping the stellar age of the Milky Way bulge with the VVV. II. Deep JKs catalogs release based on PSF photometry

Cited by in corpus (14)

• The Milky Way bar and bulge revealed by APOGEE DR16 and Gaia EDR3
• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• Variable star classification across the Galactic bulge and disc with the VISTA Variables in the Vía Láctea survey
• BAYES-LOSVD: a bayesian framework for non-parametric extraction of the line-of-sight velocity distribution of galaxies
• Orbits of globular clusters computed with dynamical friction in the Galactic anisotropic velocity dispersion field
• Age-morphology dependence of the Milky Way boxy/peanut bulge seen in Mira variables
• Comparing bulge RR Lyrae stars with bulge giants -- Insight from 3D kinematics
• Probing the Milky Way stellar and brown dwarf initial mass function with modern microlensing observations
• The small boxy/peanut structure of the Milky Way traced by old stars
• VVV catalog of ab-type RR Lyrae in the inner Galactic bulge
• The Galactic Bulge exploration IV.: RR~Lyrae stars as traces of the Galactic bar -- 3D and 5D analysis, extinction variation
• Predicted Trends in Milky Way Bulge Proper Motion Rotation Curves: future Prospects for HST and LSST
• Unveiling VVV/WISE Mira variables on the far side of the Galactic disk: Distances, kinematics and a new extinction law
• An MCMC Approach to the Three-dimensional Structure of the Milky Way Bulge using OGLE-IV $\delta$ Scuti Stars