1209.3856 (Xiaojia Zhang et al.)

Galacto-forensic of LMC's orbital history as a probe for the dark matter potential in the outskirt of the Galaxy    [PDF]

Xiaojia Zhang, Douglas N. C. Lin, Andreas Burkert, Ludwig Oser

The 3D observed velocities of the Large and Small Magellanic Clouds(LMC and SMC) provide an opportunity to probe the Galactic potential in the outskirt of the Galactic halo. Based on a canonical NFW model of the Galactic potential, Besla et al.(2007) reconstructed LMC and SMC's orbits and suggested that they are currently on their first perigalacticon passage about the Galaxy. Motivated by several recent revisions of the Sun's motion around the Galactic center, we re-examine the LMC's orbital history and show that it depends sensitively on the dark-matter's mass distribution beyond its present Galactic distance. We utilize results of numerical simulations to consider a range of possible structural and evolutionary models for the Galactic potentials. We find that within the theoretical and observational uncertainties, it is possible for the LMC to have had multiple perigalacticon passages on the Hubble time scale, especially if the Galactic circular velocity at the location of the Sun is greater than $\sim 228$km s$^{-1}$. Based on these models, a more accurate determination of the LMC's motion may be used to determine the dark matter distribution in the outskirt of the Galactic halo.

View original: http://arxiv.org/abs/1209.3856