GALACTO-FORENSIC OF LARGE MAGELLANIC CLOUD'S ORBITAL HISTORY AS A PROBE FOR THE DARK MATTER POTENTIAL IN THE OUTSKIRTS OF THE GALAXY

摘要

The three-dimensional 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. 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 timescale, especially if the Galactic circular velocity at the location of the Sun is greater than ~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.