Galactic rotation from Cepheids with Gaia DR2 and effects of non-axisymmetry
Abstract
We apply a simple axisymmetric disc model to 218 Galactic Cepheids whose accurate measurements of the distance and velocities are obtained by cross-matching an existing Cepheids catalogue with the Gaia DR2 data. Our model fit determines the `local centrifugal speed', Vc - defined as the rotation speed required to balance the local radial gravitational force - at the Sun's location to be Vc(R0) = 236 ± 3 km s-1 and the Sun's azimuthal and radial peculiar motions to be V⊙ = 12.4 ± 0.7 km s-1 and U⊙ = 7.7 ± 0.9 km s-1, respectively. These results are obtained with strong priors on the solar radius, R0 = 8.2 ± 0.1 kpc, and the Sun's angular rotation velocity, Ω⊙ = 30.24 ± 0.12 km s-1 kpc-1. We also applied the axisymmetric model to mock data from a N-body/hydrodynamic simulation of a Milky Way-like galaxy with a bar and spiral arms. We find that our axisymmetric model fit to the young stars recovers the local centrifugal speed reasonably well, even in the face of significant non-axisymmetry. However, the local centrifugal speed determined from our Cepheid sample could suffer from systematic uncertainty as large as 6 km s-1.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2019
- DOI:
- 10.1093/mnras/sty2623
- arXiv:
- arXiv:1803.05927
- Bibcode:
- 2019MNRAS.482...40K
- Keywords:
-
- methods: numerical;
- stars: variables: Cepheids;
- Galaxy: disc;
- Galaxy: fundamental parameters;
- Galaxy: kinematics and dynamics;
- solar neighbourhood;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 13 pages, 8 figures, 2 tables, accepted for publication in MNRAS