The influences of the Magellanic Clouds on the Galaxy: Pole shift, warp, and star formation history

TL;DR

This study models the dynamical influence of the Large Magellanic Cloud on the Milky Way, revealing effects like pole shift, warp formation, and minor impact on star formation, with implications for future observations.

Contribution

It provides a self-consistent N-body simulation demonstrating the LMC's effects on Galactic structure and dynamics, including pole shift and warp formation, with detailed orbital parameter calibration.

Findings

Galactic pole shift rate ~2 degrees per Gyr

Outer warp structures are formed due to LMC interaction

Star formation rate remains largely unaffected

Abstract

We investigate how the Large Magellanic Cloud (LMC) influences the evolution of the Galaxy after the LMC enters into the virial radius of the dark matter halo of the Galaxy for the first time. Both the Galaxy and the LMC are modeled as N-body particles in our models so that the dynamical influences of the LMC on the Galaxy can be investigated in a fully self-consistent manner. Furthermore, the orbital parameters for the LMC are carefully chosen such that the present location of the LMC in the Galaxy can be rather precisely reproduced in our simulations. We particularly investigate the influences of the LMC on the precession rate, the outer stellar and gaseous structures, and the star formation history of the Galaxy. Our principals results are summarized as follows. The LMC-Galaxy dynamical interaction can cause "pole shift" (or irregular precession/nutation) of the Galaxy and the typical rate of pole shift (dot {\theta}_{d}) is ~2 degree Gyr^{-1} corresponding to ~ 7 muas yr^{-1}. The LMC-Galaxy interaction induces the formation of the outer warp structures of the Galaxy, which thus confirms the results of previous numerical simulations on the formation of the Galactic warp. The LMC-Galaxy interaction also induces the formation of outer (R>20 kpc) spiral arms and increases the vertical velocity dispersion of the outer disk significantly. The mean star formation rate of the Galaxy for the last several Gyrs can be hardly influenced by the LMC's tidal force. The age and metallicity distribution of stars in the solar-neighborhood (7 kpc < R < 10 kpc) for the last several Gyr can be only slightly changed by the past LMC-Galaxy interaction. Based on these results, we discuss how the possible ongoing Galactic pole shift with 10 muas yr^{-1} can be detected by future observational studies by GAIA.