Gaia-DR2 extended kinematical maps. Part III: Rotation curves analysis, dark matter, and Modified Newtonian dynamics tests

Abstract

Recent statistical deconvolution methods have produced extended kinematical maps in a range of heliocentric distances that are a factor of two to three larger than those analysed in the Gaia Collaboration based on the same data. In this paper, we use such maps to derive the rotation curve both in the Galactic plane and in off-plane regions and to analyse the density distribution. By assuming stationary equilibrium and axisymmetry, we used the Jeans equation to derive the rotation curve. Then we fit it with density models that include both dark matter and predictions of the MOND (Modified Newtonian dynamics) theory. Since the Milky Way exhibits deviations from axisymmetry and equilibrium, we also considered corrections to the Jeans equation. To compute such corrections, we ran N-body experiments of mock disk galaxies where the departure from equilibrium becomes larger as a function of the distance from the centre. The rotation curve in the outer disk of the Milky Way that is constructed with the Jeans equation exhibits very low dependence on $R$ and $z$ and it is well-fitted both by dark matter halo and MOND models. The application of the Jeans equation for deriving the rotation curve, in the case of the systems that deviate from equilibrium and axisymmetry, introduces systematic errors that grow as a function of the amplitude of the average radial velocity. In the case of the Milky Way, we can observe that the amplitude of the radial velocity reaches $\sim 10\%$ that of the azimuthal one at $R\approx 20$ kpc. Based on this condition, using the rotation curve obtained from the Jeans equation to calculate the mass may overestimate its measurement.

11 pages, 8 figures, accepted to be published in A&A

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• The Gaia mission
• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
• On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution
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• Implications of a time-varying Galactic potential for determinations of the dynamical surface density
• Long-lived transient structure in collisionless self-gravitating systems
• Transient spiral arms from far out of equilibrium gravitational evolution

Cited by in corpus (17)

• Detection of the Keplerian decline in the Milky Way rotation curve
• Mapping the Milky Way Disk with Gaia DR3: 3D extended kinematic maps and rotation curve to $\approx 30$ kpc
• Strong constraints on the gravitational law from $Gaia$ DR3 wide binaries
• The phase spiral in Gaia DR3
• Mass models of the Milky Way and estimation of its mass from the GAIA DR3 data-set
• Constraining the Gravitational Potential from the Projected Morphology of Extragalactic Tidal Streams
• A Bayesian estimation of the Milky Way's circular velocity curve using Gaia DR3
• Modeling of Spiral Structure in a Multi-Component Milky~Way-Like Galaxy
• How Close Dark Matter Halos and MOND Are to Each Other: Three-Dimensional Tests Based on Gaia DR2
• On the Galactic rotation curve inferred from the Jeans equations Assessing its robustness using Gaia DR3 and cosmological simulations
• 3-D kinematics of classical Cepheids according to Gaia, EDR3 catalog
• Formation of disks with long-lived spiral arms from violent gravitational dynamics
• Virial theorem in clusters of galaxies with MOND
• Exact semianalytical calculation of rotation curves with Bekenstein-Milgrom nonrelativistic MOND
• Kinematics of the Milky way from the statistical analysis of the Gaia Data Release 3
• Galaxy rotation curve based on RGB stars from the Gaia DR3 catalogue
• Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess