Estimate of Current Mass of the Large Magellanic Cloud from the Orphan–Chenab Tidal Stream

Abstract By fitting the tilt in the path of the Orphan–Chenab Stream (OCS), we conclude that the current mass of the Large Magellanic Cloud (LMC) within 30 kpc is (4.7–5.1) × 10 10 M ⊙ . We note that the tidal radius of the LMC of this mass is 16.9 kpc, indicating that our measured mass approximates the current bound mass of the LMC. Previous measurements of the LMC mass based on fitting the observed path of the OCS through the Milky Way (MW) halo reported the total mass of the LMC. We show that because the closest approach of the LMC to the OCS, where the gravitational perturbation of the stream path is the highest, is about 20 kpc, the mass of the LMC outside 30 kpc is not constrained and depends entirely on the assumed radial profile at large radius. Our best-fit total mass varies between 4.5 × 10 10 and 2.2 × 10 11 M ⊙ or more, depending on the presumed radial profile of the LMC. We also show that previous measurements of the mass of the LMC that used a particle-spray method to simulate the path of the OCS suffered from systematic error because they assumed that all particles were stripped from the dwarf galaxy at the tidal radius; N -body simulations show that particles are actually released from a range of distances from the center of mass of the OCS. In contrast, the choice of MW potential has little effect on the LMC mass estimated from the OCS.