Effect of the Large Magellanic Cloud on the kinematics of Milky Way satellites and virial mass estimate
Andrey V. Kravtsov, Sophia Winney
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>Λ</mml:mi> <mml:mo>+</mml:mo> </mml:mrow> </mml:math> 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 and as high as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>1.5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>12</mml:mn> </mml:msup> <mml:mspace width="0.167em"/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:mrow> </mml:math> . We present a new halo mass estimator , where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>c</mml:mi> </mml:math> is the coefficient calibrated using satellite systems in the simulated MW-sized halos, is the variance of 3D velocities taken with the sign of the radial velocity of each satellite, and is the median halocentric distance of the satellites. We show that the estimator has only <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>s</mml:mi> <mml:mo>=</mml:mo> <mml:mn>8</mml:mn> <mml:mi>%</mml:mi> </mml:mrow> </mml:math> scatter around the median relation of the estimated and true halo masses and deviates by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mo><</mml:mo> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> </mml:mrow> </mml:math> from the median during the pericentric passage of an LMC-like subhalo. This is because and 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 , in good agreement with several recent estimates using other methods.