EFFECT OF THE LARGE MAGELLANIC CLOUD ON THE KINEMATICS OF MILKY WAY SATELLITES AND VIRIAL MASS ESTIMATE

Abstract

We present a study illustrating the effects of the passage of a Large Magellanic Cloud (LMC) mass satellite on the distance and velocity distributions of satellites in Λ+Cold Dark Matter simulations of Milky Way (MW) sized halos. In agreement with previous studies, we find that during such a passage the velocity distribution develops a high-velocity tail, which can bias velocity-based virial halo mass estimates. When the velocity distribution of MW satellites is corrected for effects of the LMC passage, it is consistent with the distributions in halos of masses as low as M200c = 8 × 1011 M⊙ and as high as 1.5 × 1012 M⊙. We present a new halo mass estimator M200c = cσ3D2r med, where c is the coefficient calibrated using satellite systems in the simulated MW-sized halos, σ3D2 is the variance of 3D velocities taken with the sign of the radial velocity of each satellite, andrmed is the median halocentric distance of the satellites. We show that the estimator has onlys = 8% scatter around the median relation of the estimated and true halo masses and deviates by < 2s from the median during the pericentric passage of an LMC-like subhalo. This is because σ3D2 andr med deviate in the opposite directions during such passages. We apply the estimator to the MW satellite system and estimate the virial mass of the Milky Way of M200c = 9.96 ± 1.45 × 1011 M⊙, in good agreement with several recent estimates using other methods.