An intriguing coincidence between the majority of vast polar structure dwarfs and a recent major merger at the M31 position

Abstract

A significant part of the Milky Way (MW) dwarf galaxies orbit within a Vast POlar Structure (VPOS), which is perpendicular to the Galactic disc and whose origin has not yet been identified. It includes the Large Magellanic Cloud (LMC) and its six dynamically associated dwarf galaxies. Andromeda Galaxy (M31) experienced a major merger two to three billion years ago, and its accurate modelling predicts that an associated tidal tail is pointing towards the Galaxy. Here, we tested a possible association between M31 tidal tail particles and MW dwarf galaxies, focusing first on the LMC and its associated dwarfs since they are less affected by ram pressure. We traced back these dwarf galaxy orbits by one billion years and calculated their association with the tidal tail particles in the 6D phase space, based on their proper motion from \textit{Gaia} DR3. We find that for low-mass MW models (total mass less than 5 $\times 10^{11}{M}_{\odot }$), the separation in the 6D space can be less than 1$\sigma$ for most of the M31 modelling, albeit with a significant degree of freedom due to the still unknown proper motion of M31. We further discover that many other dwarfs could also be associated with the M31 tidal tails if their motions had been radially slowed, as expected from the ram pressure exerted by the MW corona. This intriguing coincidence could explain the origin of the VPOS, which resulted from a matter exchange between M31 and MW.

A&A, accepted 20th December 2024, published online 04 February 2025, 10 pages, 9 figures, and Appendix A, B, C, D & E

References in corpus (23)

• galpy: A Python Library for Galactic Dynamics
• Gaia Early Data Release 3: The astrometric solution
• A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
• The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
• The orbital poles of Milky Way satellite galaxies: a rotationally supported disc-of-satellites
• Gaia early DR3 systemic motions of Local Group dwarf galaxies and orbital properties with a massive Large Magellanic Cloud
• From Tidal Dwarf Galaxies to Satellite Galaxies
• Analytical properties of Einasto dark matter haloes
• A dynamical model of the local cosmic expansion
• All-Sky Dynamical Response of the Galactic Halo to the Large Magellanic Cloud
• The Milky Way's Disk of Classical Satellite Galaxies in Light of Gaia DR2
• Detection of the Keplerian decline in the Milky Way rotation curve
• Detection of the LMC-induced sloshing of the Galactic halo
• A Milky Way with a massive, centrally concentrated thick disc: new Galactic mass models for orbit computations
• Toward a Complete Understanding of the Magellanic Stream Formation
• Which Milky Way masses are consistent with the slightly declining 5-25 kpc rotation curve?
• A portrait of the Vast Polar Structure as a young phenomenon: hints from its member satellites
• The accretion history of the Milky Way. I. How it shapes globular clusters and dwarf galaxies
• The survey of planetary nebulae in Andromeda (M31) VI. Kinematics of M31 inner-halo substructures and comparison with major-merger simulation predictions
• Lessons from the Magellanic System and its modeling
• Reassessing the proper motions of M31/M33 with Gaia DR3. Unraveling systematic uncertainties
• Dark matter fraction derived from the M31 rotation curve
• The Milky Way accretion history compared to cosmological simulations -- from bulge to dwarf galaxy infall

Cited by in corpus (1)

• The long-term stability of the Vast Polar Structure and its connection to a possible previous passage of the LMC