by A distant galaxy may shed light on dark matter.
A team of astronomers recently used light from a distant galaxy to map the distribution of dark matter along a tiny slice of space, which could bring us a step closer to understanding what this mysterious, unseen object is — or at least what it is. t.
Kindai University biologist Kaiki Taro Inoue and colleagues published their work The Astrophysical Journal.
Lighting on the Dark Side
Inoue and his colleagues used ALMA to observe how light from a distant galaxy bends as it passes through the gravitational field of a nearby massive galaxy. Astronomers often use gravitational lensing to see distant, faint objects, because the curved fabric of time around massive objects acts as a mirror to the universe. But Inoue and his colleagues were looking for something that couldn’t be seen under any magnification: dark matter.
A distant quasar – a galaxy with an actively feeding black hole – happens to lie on the far side of a line from Earth through a galaxy cluster called MG J0414+0534. As the quasar’s light passes through MG J0414, it will be lifted, bent, and split into four images, all at different angles.
By carefully examining and comparing four images of the quasar, Inoue and his colleagues were able to see the shape of the curves in spacetime that the light followed to reach their telescope. Then, the team extracted the result of all the mass they could see in MG J0414, and all the dark matter that the galaxy cluster should contain. What remained was a map of all dark matter in a straight line between Earth and the distant quasar, at a resolution of 30,000 light years.
Conceptual diagram of the gravitational lens system MG J0414+0534. Dark objects associated with lensing galaxies are shown in blue and white. Dark matter in the intergalactic space is shown in orange. The solid lines show the true paths of the radio waves bent by gravity. The dotted lines indicate the visible regions of the lensed images.
NAOJ, KT Inoue
Cosmic Cold Case
Dark matter makes up about 27 percent of the mass in our universe (the other 68 percent is dark energy, and the other 5 percent is stuff we can see and interact with), but physicists still don’t know what dark matter is. is a. As the name suggests, black matter does not shine or reflect light, and it does not absorb light. And the only way dark matter interacts with ordinary matter is through its own gravity, which appears to play an important role in shaping the structures we see in the universe, from small galaxies to large clusters. It is one of the greatest mysteries in modern cosmology (the study of how our universe formed and evolved).
Another theory is that dark matter is made up of particles traveling through space at nearly the speed of light. If this theory, called “hot dark matter,” is correct, then neutrinos may be a form of dark matter. That would make sense, because neutrinos do not interact with light, and interact with other objects only through gravity and the so-called weak nuclear force.
Another idea, called “iscold dark matter,” suggests that dark matter may be made of slow-moving particles. If so, then dark matter may be clusters of tiny black holes that formed during the first second after the Big Bang; some may be less than one thousand percent the mass of a paperclip, while others may have the mass of hundreds of thousands of stars. Cold dark matter may be made of an entirely new type of elementary particle called an axion, or something called a massive interacting particle.
Currently, many cosmologists rely on cold dark matter, because it seems to explain the universe better than hot dark matter. If the dark matter is cold, then the smaller things must grow, merge together, and form larger objects and structures; smaller galaxies, for example, should collide and form larger galaxies, which in turn form clusters of galaxies, and so on. And that’s what we see happening in the universe.
But there are still important ways in which what we see in the universe doesn’t match what theory predicts, especially on small scales. At a distance greater than 3.25 million light-years, cold dark matter appears to be ideal. But if you zoom in to smaller distances, problems start to appear. That might mean that black matter is neither hot nor cold, but somewhere in between: hot black matter, in other words.
Inoue and his colleagues measured the distribution of dark matter on a scale of about 30,000 light years, and said their results support the idea that dark matter is cold.
The blue color represents the gravitational lensing images seen by ALMA. The calculated distribution of dark matter is shown in orange; bright areas indicate high concentrations of dark matter and dark orange areas indicate low concentrations.
ALMA(ESO/NAOJ/NRAO), KT Inoue et al.
We’re going to warm up
“I think some dark heat models are governed by our results, but we need a careful analysis,” Inoue said. Inverse. “If we can enforce warm dark matter models with good accuracy then we can say that dark matter is not warm, and therefore must be cold.”
Of course, physicists should be able to measure smaller particles of dark matter than they can now. The smallest particles of dark matter we can currently detect are about 100 million times the size of our Sun. But the exact details scientists like Inoue want to uncover the composition, and thus the nature, of dark matter will require measuring tiny clumps, between 100,000 and a million times the mass of our Sun.
Meanwhile, Inoue and his colleagues are in the process of analyzing more gravitationally lensed quasars and mapping dark matter in thin slices of the sky.
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