March 3, 2024

A Massive Remnant Galaxy Without Dark Matter Astronomers

Our understanding of the universe is incomplete. Our best model requires the existence of two substances that we have not yet discovered: dark energy and dark matter. Although that is less than ideal, the model is much better than the alternatives and has great predictive power. But if they don’t behave we can make discoveries that don’t make sense – for example, a massive galaxy that doesn’t seem to contain dark matter.

The galaxy is called NGC 1277 and is located 240 million light years away. It is a giant elliptical galaxy, and a galaxy of its size should have between 10 and 70 percent of its mass as dark matter. Its stellar mass is about 150 billion times that of the Sun, that’s not a small galaxy. However, that is not what the comments seem to indicate.

Within the radius they observe, astronomers estimate that the galaxy can have no more than 5 percent of its mass as dark matter and may as well have none. This doesn’t make sense, especially since it’s a remnant galaxy: one that hasn’t changed much in the last 12 billion years.

NGC 1277 in all its dark, matterless glory

Image Credit: NASA, ESA, and M. Beasley (IAC)

“This result does not fit with the currently accepted cosmological models, including dark matter,” said lead author Sebastién Comerón, from the Instituto de Astrofísica de Canarias and the University of La Laguna, in a. statement.

“The importance of remnant galaxies in helping us understand how the first galaxies formed was the reason we decided to observe NGC 1277 with a central field spectrograph. From the spectrum we made kinematic maps that enabled us to work out the mass distribution within the galaxy to a radius of about 20,000 light years.”

The lack of dark matter within this distance from the center of the galaxy makes no sense. The scientists have put forward two possible explanations, but neither of them is satisfactory to fully explain what the team is seeing.

“One is that the dark matter has been removed by the gravitational interaction with the surrounding medium within the galaxy cluster in which this galaxy is located,” said co-author Anna Ferré-Mateu, also a researcher at the IAC and the ULL. “The other is that the dark matter was driven out of the system when the galaxy formed when protogalactic fragments merged, giving rise to the remnant galaxy.”

The lack of dark matter is certainly a problem for the standard model of cosmology and its expectations. But it’s even more of a problem for the alternative theories that get rid of the need for dark matter by changing the behavior of gravity instead.

“Although it is possible to lose the dark matter in a particular galaxy, the modified law of gravity must be universal, there can be no exceptions, so that a galaxy without dark matter is a refutation of this kind of alternatives to dark matter,” explained co-author Ignacio Trujillo, also from the IAC and ULL.

The discovery is reported in the journal Astronomy & Astrophysics.

Leave a Reply

Your email address will not be published. Required fields are marked *