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Clash with Antlia 2 formed ripples of the outer disk of the Milky Way

The outer disk of the Milky Way characterized by various gaseous ripples that have been studied over the years. The cause that generated them was not fully identified and a new study, conducted by Sukanya Chakrabarti, a researcher at the Rochester Institute of Technology, puts a new theory on the table regarding their formation.

These ripples would have been produced by a collision in the past between the Milky Way and the dwarf galaxy Antlia 2, a galaxy with dimensions similar to those of the Great Magellanic cloud but much weaker at a diluminosity level so that it is defined as a dark galaxy. Analyzing the data produced by the Gaia mission of the European Space Agency, a researcher was able to understand that Antlia 2 crashed at some point in the past against the Milky Way producing the large ripples in the external gas disk that we see today.

Further data produced by Gaia will make this theory even clearer. Among other things, this work could also help to understand from what dark matter can be made, as Chakrabarti explains: “If Antlia 2 is the dwarf galaxy we had foreseen, you know what its orbit should be. You know it must have come close to the galactic disk. This places stringent constraints, therefore, not only on the mass, but also on its density profile. This means that in the end it is possible to use Antlia 2 as a unique laboratory to learn about the nature of dark matter.”

This is not the only theory concerning the external ripples of the Milky Way: in this work, however, the researchers have excluded the other major ones. For example, the tidal force of Sagittarius’s elliptical dwarf galaxy is judged by the researchers to be insufficient, while the large Magellanic Cloud and the Small Magellanic Cloud are too far apart to have a gravitational effect on the outer material of the Milky Way.