Well-known galaxy model under scanner

The accepted model of galaxy formation that predicts that dwarf galaxies should form inside of small clumps of dark matter and that these clumps should be distributed randomly about their parent galaxy does not hold much water, says an analysis of the model by astrophysicists.

"What is observed is very different. The dwarf galaxies belonging to the Milky Way and Andromeda are seen to be orbiting in huge, thin disk-like structures," said David Merritt, a professor of astrophysics at Rochester Institute of Technology in the US.

Dwarf galaxies that orbit the Milky Way and the Andromeda galaxies defy the accepted model of galaxy formation, and recent attempts to wedge them into the model are flawed, the study showed.

The study pokes holes in the current understanding of galaxy formation and questions the accepted model of the origin and evolution of the universe.

To prove their point, researchers looked at three recent papers by different international teams, all of which concluded that the satellite galaxies support the standard model.

A team of 14 scientists from six different countries replicated the earlier analyses using the same data and cosmological simulations and came up with much lower probabilities - roughly one tenth of a percent - that such structures would be seen in the Milky Way and the Andromeda galaxy.

"Our conclusion tends to favour an alternate, and much older, model: that the satellites were pulled out from another galaxy when it interacted with the Local Group galaxies in the distant past," Merritt noted.

This 'tidal' model can naturally explain why the observed satellites are orbiting in thin disks, he added.

The study will appear in a forthcoming issue of the journal Monthly Notices of the Royal Astronomical Society.