The AGC 114905 is a universe. The emission of the stars is blue. The clouds are green. After 40 hours of detailed observations with state-of-the-art telescopes, the galaxy does not appear to have dark matter. Credit is given to: Javier Romn & Pavel Mancera Pia.
A team of researchers from the Netherlands have found no trace of dark matter in the AGC 114905 despite using state-of-the-art telescopes. They will give their findings in monthly Notices of the Royal Astronomical Society.
When they discovered six galaxies with little to no dark matter, they were told to "measure again, you'll see that there will be dark matter around your galaxy". The evidence for a dark matter-free galaxy only became stronger after four hours of detailed observations using the Very Large Array.
AGC 114905 is about 250 million light-years away. It is classified as an ultra-diffuse dwarf galaxy, with the name 'dwarf galaxy' referring to its luminosity and not to its size. Our own Milky Way contains more than 100 stars, but the galaxy contains a thousand less. The idea is that all galaxies and dwarf galaxies can only exist if they are held together by dark matter.
The researchers used the VLA telescope to collect data on the rotation of gas in AGC 114905. The distance of the gas from the center of the galaxy to the x- axis and the rotation speed of the gas on the y- axis were shown in a graph. This is a way to show the presence of dark matter. The motions of the gas in AGC 114905 can be explained by normal matter.
"This is what we thought and hoped for, and it confirms our previous measurements," says Mancera Pia. The problem is that the theory predicts dark matter in AGC 114905, but we don't see it. The difference between theory and observation is getting bigger.
The researchers have a list of possible explanations for the lack of dark matter. AGC 114905 could have been stripped of dark matter by a large nearby galaxies. Mancera Pia said there were no. Extreme parameters would have to be introduced in the so called cold dark matter model in order to be considered in the most reputed galaxy formation framework. We can't reproduce the motions of the gas within the galaxy with modifiedNewtonian dynamics.
The researchers say there is one more assumption that could change their conclusions. They think they are looking at the galaxy at an angle. Tom says that the angle has to deviate from the estimate before there is room for dark matter again.
The researchers are looking at a second dwarf galaxy. If there is no trace of dark matter in that galaxy again, it will make the case for dark matter even stronger.
The research of Mancera Pia is not the only one. The Dutch American, Pieter van Dokkum, discovered a galaxy with hardly any dark matter. Mancera Pia and her colleagues have more robust techniques.
There is no need for dark matter in the resolved kinematics of the ultra-diffuse galaxy AGC 114905. Monthly Notices of the Royal Astronomical Society are accepted for publication.
There are monthly Notices of the Royal Astronomical Society.
Evidence emerged for dark-matter free galaxies on December 6th, 2021.
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