The Collision Between The Milky Way And Andromeda

Given that this is a topic that arises occasionally in this group:


arXiv:0705.1170
Title: The Collision Between The Milky Way And Andromeda
Authors: T.J. Cox, Abraham Loeb (Harvard/CfA)
Comments: submitted to MNRAS

We use a N-body/hydrodynamic simulation to forecast the future
encounter between the Milky Way and the Andromeda galaxies, given
current observational constraints on their relative distance, relative
velocity, and masses. Allowing for a comparable amount of diffuse mass
to fill the volume of the Local Group, we find that the two galaxies
are likely to collide in a few billion years - within the Sun's
lifetime. During the first close encounter of the two galaxies, there
is a 12% chance that the Sun will be pulled from its present position
and reside in the extended tidal material. After the second close
encounter, there is a 30% chance that the Sun will reside in the
extended tidal material, and a 2.7% chance that our Sun will be more
tightly bound to Andromeda than to the Milky Way. Eventually, after
the merger has completed, the Sun is likely to be scattered to the
outer halo and reside at much larger radii (30 kpc). The density
profiles of the stars, gas and dark matter in the merger product
resemble those of elliptical galaxies. Our Local Group model therefore
provides a prototype progenitor of late--forming elliptical galaxies.

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