Even after 40 hours of additional sharp measurement, there is no trace of dark matter in AGC 114905

An international team of researchers led by Groningen found no trace of dark matter in AGC 114905 even after 40 hours of measurement with very good telescopes, and they will soon publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Take another good measure, because then you will see that there is dark matter around your galaxy. Pavel Mancera Peña (University of Groningen and Astron) and colleagues learned this after discovering six galaxies with little or no dark matter at the end of 2019. But after another forty hours of measurements with the Very Large Array in New Mexico, the evidence for The existence of a galaxy devoid of dark matter is only stronger.

The galaxy in question is AGC 114905, about 250 million light-years away. It is the so-called super-dwarf galaxy. The name of the dwarf galaxy refers to the dimming of the light, not its size. The galaxy is roughly the size of our Milky Way, but contains a thousand times fewer stars. The prevailing idea is that all galaxies, especially super-dwarf galaxies, can exist only if they are held together by dark matter.

Rotational speed in the graph
Using the VLA telescope, the researchers collected 40 hours of data about the gas rotation of AGC 114905 between July and October 2020, then plotted the x-axis of the gas’s distance from the galactic center. Gas. This is a tried and true method for detecting dark matter. The graph shows that the rotational velocity of the gas in AGC 114905 can be fully explained using only ordinary matter.

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“This is of course what we had thought and hoped for, because it confirms our previous measurements.” “Yes, the problem now remains that theory predicts that there should be dark matter in AGC 114905, but our observations say there is no. In fact, the difference between theory and observation is getting larger,” says Pavel Mancera Peña.

Possible explanations
In their scientific publications, researchers go through the possible explanations for the lack of dark matter one by one. For example, AGC 114905 could have been stripped of dark matter by large nearby galaxies. Mancera Peña: “But there is nothing. And in the most famous framework of galaxy formation, the so-called cold dark matter model, we will have to enter extreme parameter values ​​that fall outside the usual range. Also with Modified Newton dynamicsAlternative theory, we cannot reproduce the motions of gas.”

According to the researchers, there could be another assumption that could throw a wrench into the works. This is the approximate angle at which they think they see the galaxy. “But this tilt angle would have to be very different from our estimate if there is room for dark matter again,” said co-author Tom Osterloo (ASTRON).

Research does not stand alone
Meanwhile, researchers are examining a second, super-diffused dwarf galaxy in detail. If no traces of dark matter appear in that galaxy either, this makes the case for dark matter poor galaxies even stronger.

The investigations by Mancera Peña and colleagues are not isolated. Earlier, for example, Dutch-American Peter van Dokkum (Yale University, USA) discovered a galaxy with barely any dark matter. The Mancera Piña team’s technique and measurements are more accurate.

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Scientific material
No Need for Dark Matter: The Kinetics of Resolving a Super-Diffused Galaxy AGC 114905. Section: Pavel E. Mancera Peña (1,2), Filippo Fraternali (1), Tom Osterlo (2), Elizabeth AK Adams (2,1), Kyle A. Amman (3) and Lucas Lisman (4,5). Geaccepteerd voor publicatie in Monthly Notices of the Royal Astronomical Society. (Free Advance Version)

1. Captain Institute, University of Groningen
2. Astron, Netherlands Institute for Radio Astronomy
3. Institute of Computational Cosmology, Department of Physics, Durham University, Feringed Koninkrijk
4. Department of Physics and Astronomy, Valparaiso University, Indiana, Verenigde Staten

Galaxy AGC 114905. A stellar emission from the galaxy is shown in blue. Green clouds show neutral hydrogen gas. Even after 40 hours of measurement with very good telescopes, the galaxy does not appear to contain any dark matter. (c) Javier Roman and Pavel Mancera Pena

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