Quadrupole signature as a kinematic diagnostic to constrain bar properties : implications for the Milky Way

Abstract

The presence of a 'butterfly' or a quadrupole structure in the stellar mean radial velocity ($<V_R>$) field of the Milky Way is well known from the Gaia and the APOGEE surveys. Past studies indicated that a stellar bar can excite such a quadrupole feature in the $<V_R>$ distribution. However, a systematic study investigating the co-evolution of bar and quadrupole structure is largely missing. Furthermore, whether this quadrupole structure in $<V_R>$ can be used as a robust kinematic diagnostic to constrain bar properties, particularly for the Milky Way, is still beyond our grasp. Here, we investigate the bar-induced quadrupole feature using a suite of isolated $N$-body models forming prominent bars and a sample of Milky Way-like barred galaxies from the TNG50 cosmological simulation. We demonstrate that the properties of the quadrupole (strength, length, and orientation) are strongly correlated with the bar properties, regardless of the choice of the thin/thick disc stars; thereby making the quadrupole feature an excellent kinematic diagnostic for constraining the bar properties. In presence of spirals, the estimator which takes into account the phase-angle of $m=4$ Fourier moment, serves as a more appropriate estimator for measuring the length of the quadrupole. Further, we constructed a novel Gaia-like mock dataset from a simulated bar model while incorporating the dust extinction and the broad trends of observational errors of the Gaia survey. The quadrupole properties (strength and length) estimated from those Gaia-like mock data are larger ($\sim 35-45$ percent) when compared with their true values. We showed that the majority of this effect is due to the uncertainty in parallax measurement. This demonstrates that the quadrupole structure in Gaia data is likely a result of dominant Gaia parallax errors/biases, almost masking the true inherent signature of the MW bar.

arXiv comment15 pages, 1 table, 13 figures (including appendix), accepted for publication in A&A

References in corpus (60)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• Simulating Galaxy Formation with the IllustrisTNG Model
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Simulating galaxy formation with black hole driven thermal and kinetic feedback
• First Results from the TNG50 Simulation: Galactic outflows driven by supernovae and black hole feedback
• First Results from the TNG50 Simulation: The evolution of stellar and gaseous disks across cosmic time
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Dynamics of Barred Galaxies
• The Effect of the Outer Lindblad Resonance of the Galactic Bar on the Local Stellar Velocity Distribution
• Vertical waves in the solar neighbourhood in Gaia DR2
• Gaia Data Release 2: Mapping the Milky Way disc kinematics
• Mapping the Three-Dimensional Density of the Galactic Bulge with VVV Red Clump Stars
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The Structure of the Milky Way's Bar Outside the Bulge
• The photometric structure of the inner Galaxy
• Secular Evolution Via Bar-Driven Gas Inflow: Results from BIMA SONG
• The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
• Gas Dynamics in the Milky Way: Second Pattern Speed and Large-Scale Morphology
• Life in the fast lane: a direct view of the dynamics, formation, and evolution of the Milky Way's bar
• Separation of Stellar Populations by an Evolving Bar: Implications for the Bulge of the Milky Way
• Signatures of radial migration in barred galaxies: Azimuthal variations in the metallicity distribution of old stars
• Detection of the old stellar component of the major Galactic bar
• The pattern speed of the Milky Way bar from transverse velocities
• Gaia Data Release 3: Mapping the asymmetric disc of the Milky Way
• A sharper view of Pal 5's tails: Discovery of stream perturbations with a novel non-parametric technique
• Constraints on the Galactic Bar from the Hercules stream as traced with RAVE across the Galaxy
• The echo of the bar buckling: phase-space spirals in Gaia DR2
• The Milky Way bar and bulge revealed by APOGEE DR16 and Gaia EDR3
• Gas flow in barred potentials - III. Effects of varying the Quadrupole
• The properties of the local spiral arms from RAVE data: two-dimensional density wave approach
• Formation and evolution of galactic disks with a multiphase numerical model
• Detection of a radial velocity gradient in the extended local disc with RAVE
• The signatures of the resonances of a large Galactic bar in local velocity space
• Fluctuations in galactic bar parameters due to bar-spiral interaction
• The disc origin of the Milky Way bulge: Dissecting the chemo-morphological relations using N-body simulations and APOGEE
• Quantifying stellar radial migration in an N-body simulation: blurring, churning, and the outer regions of galaxy discs
• The Pattern Speed of the OH/IR Stars in the Milky Way
• Gas dynamics in the Milky Way: a low pattern speed model
• An Iterative Method for Constructing Equilibrium Phase Models of Stellar Systems
• Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space
• The parallax zero point offset from Gaia EDR3 data
• Gas Dynamics in the Galaxy: Total Mass Distribution and the Bar Pattern Speed
• Variations in the width, density, and direction of the Palomar 5 tidal tails
• Hic sunt dracones: Cartography of the Milky Way spiral arms and bar resonances with Gaia Data Release 2
• Effect of bars on the galaxy properties
• The vertical effects of disc non-axisymmetries from perturbation theory: the case of the Galactic bar
• Spending too much time at the Galactic bar: chaotic fanning of the Ophiuchus stream
• Escapees from the bar resonances. On the presence of low-eccentricity, metal-rich stars at the Solar vicinity
• Dynamically constraining the length of the Milky Way bar
• Evidence of Bar-induced Secular Evolution in the Inner Regions of Stellar Discs in Galaxies: What Shapes Disc Galaxies?
• Bars and boxy/peanut bulges in thin and thick discs. II. Can bars form in hot thick discs?
• Numerical code for multi-component galaxies: from N-body to chemistry and magnetic fields
• Timing the Milky Way bar formation and the accompanying radial migration episode
• Looking for a needle in a haystack: Measuring the length of a stellar bar
• Characterising the Gaia Radial Velocity sample selection function in its native photometry
• Bars and boxy/peanut bulges in thin and thick discs III. Boxy/peanut bulge formation and evolution in presence of thick discs
• The pattern speeds of vertical breathing waves
• Quantifying the influence of bars on action-based dynamical modelling of disc galaxies
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data I. Method validation