Astronomers from the Netherlands, the United Kingdom and the United States have discovered no hint of darkish matter in AGC 114905, a gas-rich ultra-diffuse galaxy roughly 248 million light-years from Earth.
This picture exhibits the gas-rich ultra-diffuse galaxy AGC 114905; the stellar emission is proven in blue; the inexperienced clouds present the impartial hydrogen fuel. Image credit score: Javier Román / Pavel Mancera Piña.
AGC 114905 is situated about 76 megaparsecs (248 million light-years) away within the constellation of Pisces.
It is assessed as an ultra-diffuse dwarf galaxy, with the identify ‘dwarf galaxy’ referring to its luminosity and to not its dimension.
AGC 114905 is in regards to the dimension of our personal Milky Way Galaxy however accommodates a thousand occasions fewer stars.
The prevailing concept is that every one galaxies, and definitely ultra-diffuse dwarf galaxies, can solely exist if they’re held collectively by darkish matter.
“When we discovered six galaxies with little to no dark matter, we were told ‘measure again, you’ll see that there will be dark matter around your galaxy’,” stated Dr. Pavel Mancera Piña, an astronomer on the University of Groningen and ASTRON.
“However, after fourty hours of detailed observations, the evidence for a dark matter-free galaxy only became stronger.”
The researchers collected information on the rotation of hydrogen in AGC 114905 between July and October 2020 utilizing the Karl G. Jansky Very Large Array.
Subsequently, they made a graph displaying the space of the fuel from the middle of the galaxy on the X-axis and the rotation pace of the fuel on the Y-axis. This is a normal option to reveal the presence of darkish matter.
The graph exhibits that the motions of the fuel in AGC 114905 may be utterly defined by simply regular matter.
“This is, of course, what we thought and hoped for because it confirms our previous measurements,” Dr. Mancera Piña stated.
“But now the problem remains that the theory predicts that there must be dark matter in AGC 114905, but our observations say there isn’t. In fact, the difference between theory and observation is only getting bigger.”
In their paper, the authors listing the potential explanations for the shortage of darkish matter one after the other.
“For example, AGC 114905 could have been stripped of dark matter by large nearby galaxies,” they stated.
“But there are none. And in the most reputed galaxy formation framework, the so-called cold dark matter model, we would have to introduce extreme parameter values that are far beyond the usual range.”
“Also with modified Newtonian dynamics, an alternative theory to cold dark matter, we cannot reproduce the motions of the gas within the galaxy.”
There is yet another assumption that would change the conclusions. That is the estimated angle at which they assume the crew is observing the galaxy.
“But that angle has to deviate very much from our estimate before there is room for dark matter again,” stated Dr. Tom Oosterloo, an astronomer at ASTRON.
The crew’s paper shall be revealed within the Monthly Notices of the Royal Astronomical Society.
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Pavel E. Mancera Piña et al. No want for darkish matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905. MNRAS, in press; arXiv: 2112.00017
