A single-merger scenario for the formation of the giant stream and the warp of M31

TL;DR

This study uses N-body simulations to propose that the giant stream and warp of M31 resulted from the accretion of a dark-matter-rich dwarf galaxy, explaining observed features and satellite alignments.

Contribution

It introduces a cosmologically-motivated single-merger model that accounts for M31's features, supported by extensive simulations and observational data.

Findings

The model reproduces the giant stream and warp of M31.

The disrupted satellite likely resides in the North-Eastern shelf.

Surviving satellites may have been accreted from an intergalactic filament.

Abstract

We propose that the accretion of a dwarf spheroidal galaxy provides a common origin for the giant southern stream and the warp of M31. We run about 40 full N-body simulations with live M31, infalling galaxies with varying masses and density profiles, and cosmologically-plausible initial orbital parameters. Excellent agreement with a full range of observational data is obtained for a model in which a dark-matter-rich dwarf spheroidal, whose trajectory lies on the thin plane of corotating satellites of M31, is accreted from its turnaround radius of about 200 kpcs into M31 at approximately 3 Gyrs ago. The satellite is disrupted as it orbits in the potential well of the galaxy and forms the giant stream and in return heats and warps the disk of M31. We show that our cosmologically-motivated model is favoured by the kinematic data over the phenomenological models in which the satellite starts its infall from a close distance of M31. Our model predicts that the remnant of the disrupted satellite resides in the region of the North-Eastern shelf of M31. The results here suggest that the surviving satellites of M31 that orbit on the same thin plane, as the disrupted satellite once did, could have all been accreted from an intergalactic filament.