Issue |
A&A
Volume 642, October 2020
|
|
---|---|---|
Article Number | A95 | |
Number of page(s) | 9 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202038736 | |
Published online | 09 October 2020 |
Gaia-DR2 extended kinematical maps
III. Rotation curves analysis, dark matter, and MOND tests
1
Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
e-mail: zofiachrobakova@gmail.com
2
Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
3
Centro Ricerche Enrico Fermi, Via Panisperna 89A, 00184 Rome, Italy
4
Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, 00185 Roma, Italia
5
Istituto Nazionale Fisica Nucleare, Unità Roma 1, 00185 Roma, Italia
6
South-Western Institute for Astronomy Research, Yunnan University, Kunming 650500, PR China
7
Department of Astronomy, China West Normal University, Nanchong 637009, PR China
8
Faculty of Mathematics, Physics, and Informatics, Comenius University, Mlynská dolina, 842 48 Bratislava, Slovakia
Received:
24
June
2020
Accepted:
21
July
2020
Context. 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 Gaia Collaboration (2018, A&A, 616, A11) based on the same data.
Aims. 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.
Methods. 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.
Results. 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 ∼10% that of the azimuthal one at R ≈ 20 kpc. Based on this condition, using the rotation curve obtained from the Jeans equation to calculate the mass may overestimate its measurement.
Key words: Galaxy: disk / Galaxy: kinematics and dynamics
© ESO 2020
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.