A dynamical model of the local cosmic expansion

作者：Penarrubia Jorge^*; Ma Yin Zhe; Walker Matthew G; McConnachie Alan

来源：Monthly Notices of the Royal Astronomical Society, 2014, 443(3): 2204-2222.

DOI：10.1093/mnras/stu879

• Galaxy: fundamental parameters
• Galaxy: kinematics and dynamics
• Local Group
• cosmological parameters
• dark energy
• dark matter

We combine the equations of motion that govern the dynamics of galaxies in the local volume with Bayesian techniques in order to fit orbits to published distances and velocities of galaxies within 3 Mpc. We find a Local Group (LG) mass 2.3 +/- 0.7 x 10(12)M(circle dot) that is consistent with the combined dynamical masses of M31 and the Milky Way, and a mass ratio 0.54(-0.17)(+0.23) that rules out models where our Galaxy is more massive than M31 with similar to 95 per cent confidence. The Milky Way's circular velocity at the solar radius is relatively high, 245 +/- 23 km s(-1), which helps to reconcile the mass derived from the local Hubble flow with the larger value suggested by the 'timing argument'. Adopting Planck's bounds on Omega(Lambda) yields a (local) Hubble constant H-0 = 67 +/- 5 kms(-1) Mpc(-1) which is consistent with the value found on cosmological scales. Restricted N-body experiments show that substructures tend to fall on to the LG along the Milky Way-M31 axis, where the quadrupole attraction is maximum. Tests against mock data indicate that neglecting this effect slightly overestimates the LG mass without biasing the rest of model parameters. We also show that both the time dependence of the LG potential and the cosmological constant have little impact on the observed local Hubble flow.

• 出版日期2014-9-21