The Cannibal Next Door

SIfA Professor Geraint Lewis and his international team,  including with SIfA PhD students Zhen Wen, have unravelled the cannibalistic past of the Andromeda galaxy. This study, published in Nature, analysed globular cluster data from the Pan-Andromeda Archaeological Survey (PAndAS) to reconstruct the times when Andromeda devoured small galaxies to grow its stellar halo.

 “By tracing the faint remains of these smaller galaxies with embedded star clusters, we’ve been able to recreate the way Andromeda drew them in and ultimately enveloped them at the different times,” said ANU researcher Dr Dougal Mackey, who co-led the study.

Video Credit: Sebastian Zentilomo

Professor Lewis and Dr Mackey are also members of a team that a few years ago discovered the ‘plane of satellites’, an unexpected alignment of dwarf galaxies orbiting Andromeda. This plane is known to be unstable and fated to be destroyed by the Andromeda’s gravitational field.

“This deepens the mystery as the plane must be young, but it appears to be aligned with ancient feeding of dwarf galaxies. Maybe this is because of the cosmic web, but really, this is only speculation. We’re going to have to think quite hard to unravel what this is telling us,” Professor Lewis said.

Read the full story University of Sydney Media Release.