Response of the Milky Way's disc to the Large Magellanic Cloud in a first infall scenario

TL;DR

This study uses simulations to show how the Large Magellanic Cloud's infall can cause significant warping in the Milky Way's disc, aligning with observed features and suggesting satellite interactions shape galactic structures.

Contribution

It provides the first detailed simulation-based analysis of the LMC's impact on the Milky Way's disc during a first infall scenario, matching observed warp features.

Findings

LMC can induce strong disc warps consistent with observations

The most massive LMC model best explains the warp features

Satellite interactions likely contribute to the Milky Way's disc heating

Abstract

We present N-body and hydrodynamical simulations of the response of the Milky Way's baryonic disc to the presence of the Large Magellanic Cloud during a first infall scenario. For a fiducial galactic model reproducing the gross properties of the Galaxy, we explore a set of six initial conditions for the LMC of varying mass which all evolve to fit the measured constraints on its current position and velocity with respect to the Galactic Center. We find that the LMC can produce strong disturbances - warping of the stellar and gaseous discs - in the Galaxy, without violating constraints from the phase-space distribution of stars in the Solar Neighbourhood. All models correctly reproduce the phases of the warp and its anti-symmetrical shape about the disc's mid-plane. If the warp is due to the LMC alone, then the largest mass model is favoured ($2.5\times10^{11}\,\rm{M_{\odot}}$). Still, some quantitative discrepancies remain, including deficits in height of $\Delta Z=0.7 \, \rm{kpc}$ at $R=22 \,\rm{kpc}$ and $\Delta Z=0.7\, \rm{kpc}$ at $R=16 \,\rm{kpc}$. This suggests that even higher infall masses for the LMC's halo are allowed by the data. A comparison with the vertical perturbations induced by a heavy Sagittarius dSph model ($10^{11}\,\rm{M_{\odot}}$) suggest that positive interference with the LMC warp is expected at $R=16 \, \rm{kpc}$. We conclude that the vertical structure of the Galactic disc beyond the Solar Neighbourhood may jointly be shaped by its most massive satellites. As such, the current structure of the MW suggests we are seeing the process of disc heating by satellite interactions in action.