Researchers, affiliated with several institutions in China, have found evidence of more dark-matter-deficient dwarf galaxies. The team of researchers stated their findings of how some of the dwarf galaxies, which they expected to be dominated by dark matter, were not up to the mark, in a paper published in the journal Nature Astronomy.

According to the researchers, the standard cosmological theory states that dark matter drives formation of galaxies and the gravity wells in which they form. The paper suggests that the dwarf galaxies in the local group, the ones those in our part of the universe, are dominated by dark matter.

Dwarf galaxy
Dark matter of dwarf galaxy CC0 Public Domain

In 2017, two dwarf galaxies were found to have less dark matter than it was expected.Following that, another team observed two more dwarf galaxies and now, the researchers have identified 19 more dwarf galaxies with amounts of dark matter that do not follow the theory.

The researchers said that they analysed the data from the Arecibo radio telescope to calculate the galactic weights. However, this can also be done by measuring how fast hydrogen moves around the galaxies and the higher the speed, the more mass a galaxy will have.

Phys.org quoted the researchers as saying that the total mass of all the stars (using starlight data) and the hydrogen should come up with a total of non-dark matter mass for the galaxy. The difference between this number and the total mass was attributable to dark matter.

Findings can challenge formation theory

The report said that in 'normal' cases, only 2 percent of dwarf galaxy's mass is made up of non-dark matter. But in case of their study, the team found "what they describe as oddballs—one galaxy, for example, weighed in at approximately 14 billion suns, and its total non-dark matter mass made up approximately 27 percent of its total mass".

The group of researchers analysed a total of 324 dwarf galaxies and 19 dwarf galaxies were found to have less dark matter than what the theory suggested.

The scientists suggested that the "missing" dark matter of those dwarf galaxies may be attributed to its nearby ones that must have pulled it off. But, surprisingly they found a few exceptions which had no neighbours that were close enough to be considered as suspects.

The team believes that these findings can challenge the formation theory as it is applicable for dwarf galaxies.