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The Milky Way - Large Magellanic Cloud Interaction with Simulation Based Inference

RAN Brooks, JL Sanders, V Chandra… - arXiv preprint arXiv …, 2025 - arxiv.org
Astrophysics paper astro-ph.GA Suggest

… We use a Simulation Based Inference framework to constrain properties of the MW, LMC and the induced reflex motion using the dynamics of outer MW halo stars. …

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@article{2510.04735v1,
Author        = {Richard A. N. Brooks and Jason L. Sanders and Vedant Chandra and Nicolás Garavito-Camargo and Adam M. Dillamore and Adrian M. Price-Whelan and Yuan-Sen Ting},
Title         = {The Milky Way - Large Magellanic Cloud Interaction with Simulation Based
  Inference},
Eprint        = {2510.04735v1},
ArchivePrefix = {arXiv},
PrimaryClass  = {astro-ph.GA},
Abstract      = {The infall of the Large Magellanic Cloud (LMC) into the Milky Way (MW) has
displaced the MW's centre of mass, manifesting as an observed reflex motion in
the velocities of outer halo stars. We use a Simulation Based Inference
framework to constrain properties of the MW, LMC and the induced reflex motion
using the dynamics of outer MW halo stars. Specifically, we use the mean radial
and tangential velocities of outer halo stars calculated in a set of distance
and on-sky bins. We train neural networks to estimate parameter posterior
distributions using a set of $128,000$ rigid MW--LMC simulations conditioned
upon velocity data from the Dark Energy Spectroscopic Instrument (DESI) and the
combined H3+SEGUE+MagE outer halo surveys. We constrain the reflex motion
velocity and the enclosed MW and LMC masses within $50 \, \rm kpc$ using the
DESI or H3+SEGUE+MagE dataset while varying the survey sky coverage and depth.
We find the most precise constraints by using the radial and tangential
velocity data from the H3+SEGUE+MagE survey and on-sky quadrant sky coverages.
We report a reflex motion velocity, the speed at which the MW lurches towards
the LMC, of $v_{\rm{travel}} = 26.4^{+5.5}_{-4.4} \, \rm km \, \rm s^{-1}$,
while simultaneously finding an enclosed LMC mass of $M_{\rm LMC}(< 50 \, \rm
kpc) = 9.2^{+1.9}_{-2.3} \times 10^{10}\, \rm M_{\odot}$ and enclosed MW mass
of $M_{\rm MW}(< 50 \, \rm kpc) = 4.4^{+0.7}_{-0.7} \times 10^{11}\, \rm
M_{\odot}$. Our results suggest that the LMC's total mass is at least $\approx
10-15 \%$ of that of the MW. This inference framework is flexible such that it
can provide rapid and reliable constraints when applied to any future survey
measuring the velocities of outer halo stars.},
Year          = {2025},
Month         = {Oct},
Url           = {http://arxiv.org/abs/2510.04735v1},
File          = {2510.04735v1.pdf}
}

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