Influence of the cosmological constant on the motion of Magellanic Clouds in the gravitational field of Milky Way
Abstract
Using the pseudoNewtonian (PN) potential reflecting properties of the Schwarzschildde Sitter spacetime, we estimate the influence of the repulsive cosmological constant Λ ~ 1.3 × 10^{56}cm^{2} implied by recent cosmological tests onto the motion of both Small and Large Magellanic Clouds (SMC and LMC) in the gravitational field of the Milky Way. Considering detailed modelling of the gravitational field of the Galaxy disc, bulge and cold dark matter halo, the trajectories of SMC and LMC constructed for the PN potential with the cosmological constant are confronted to those given for Λ = 0. In the realistic model of the extended cold dark matter halo its edge and related total mass are taken at typical values reflecting recent diversity in the total Galaxy mass estimates. In all cases, strong influence of the cosmological constant, on 10% level or higher, has been found for motion of both SMC and LMC. Inside the halo, the Newtonian part of the PN potential is exact enough, while outside the halo the PN potential can give relevant relativistic corrections. The role of the cosmological constant is most conspicuous when binding mass is estimated for the satellite galaxies. We have found a strong influence of cosmic repulsion on the total binding mass for both galaxies. For SMC there is the binding mass M_{SMC}^{Λ = 0} = 7.07 × 10^{11}M_{⨀} and M_{SMC}^{Λ > 0} = 8.61 × 10^{11}M_{⨀}, while even much higher increase is found for LMC, where M_{LMC}^{Λ = 0} = 1.50 × 10^{12}M_{⨀} and M_{LMC}^{Λ > 0} = 2.21 × 10^{12}M_{⨀}, putting serious doubts on the possibility that the LMC is bounded by the Milky Way. However, the estimates of binding masses are strongly influenced by initial velocity of SMC and LMC; we took the values inferred for the IAU MW rotation velocity ~ 220 km/s. Our results indicate very important role of the cosmic repulsion in the motion of interacting galaxies, clearly demonstrated in the case of the satellite SMC and LMC galaxies moving in the field of Milky Way. In some cases, the effect of the cosmic repulsion can be even comparable to the effects of the dynamical friction and the Andromeda Galaxy.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 September 2011
 DOI:
 10.1088/14757516/2011/09/018
 Bibcode:
 2011JCAP...09..018S