New Observations of Satellite Galaxies Reveal Models May be Wrong

Satellite galaxies move in rotating discs around larger ones. Yet these galaxies aren't predicted by current models, leaving astronomers baffled. Now, scientists have taken a closer look at satellite galaxies in an attempt to explain why the models don't reflect reality.

Researchers have long known of the existence of numerous dwarf galaxies around larger ones, like our own Milky Way. Yet in the past few years, the movement of these galaxies has raised a number of questions of interpretation. This is mostly due to the fact that the orbits are arranged in large, flat rotating structures. That's in stark contrast to our best current models of galaxy formation, which predict that they should move in all directions.

In order to look at these galaxies a bit more closely and find out the truth, scientists looked at data from the Sloan Digital Sky Survey. In all, they analyzed 380 galaxies located between 30 and 700 million light-years away. All of these had at least two visible satellite galaxies that appeared to orbit around their hosts.

In the end, the researchers found that about half of the satellite galaxies must be located in rotating discs in order to agree with their observations. This, in turn, means that current models are incorrect.t

The findings call into question the predictions of the standard model at galactic scales. This is due to the fact that if this phenomenon were linked to the accretion of satellite galaxies along filaments of dark matter in the universe, it would be necessary to explain why these rotating structures are much thinner than the filaments that gave rise to them, and also why the two brightest satellite galaxies systematically always come from the same filament.

The findings are published in the journal Nature.