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Durham University

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Publication details for Dr Alis Deason

Cautun, Marius, Deason, Alis J, Frenk, Carlos S & McAlpine, Stuart (2019). The aftermath of the Great Collision between our Galaxy and the Large Magellanic Cloud. Monthly Notices of the Royal Astronomical Society 483(2): 2185-2196.

Author(s) from Durham


The Milky Way (MW) offers a uniquely detailed view of galactic structure and is often regarded
as a prototypical spiral galaxy. But recent observations indicate that the MW is atypical: it
has an undersized supermassive black hole at its centre; it is surrounded by a very low mass,
excessively metal-poor stellar halo; and it has an unusually large nearby satellite galaxy, the
Large Magellanic Cloud (LMC). Here, we show that the LMC is on a collision course with the
MW with which it will merge in 2.4+1.2 −0.8 Gyr (68 per cent confidence level). This catastrophic
and long-overdue event will restore the MW to normality. Using the EAGLE galaxy formation
simulation, we show that, as a result of the merger, the central supermassive black hole will
increase in mass by up to a factor of 8. The Galactic stellar halo will undergo an equally
impressive transformation, becoming 5 times more massive. The additional stars will come
predominantly from the disrupted LMC, but a sizeable number will be ejected on to the halo
from the stellar disc. The post-merger stellar halo will have the median metallicity of the LMC,


= −0.5 dex, which is typical of other galaxies of similar mass to the MW. At the end
of this exceptional event, the MW will become a true benchmark for spiral galaxies, at least