The dark matter around some of the earliest and most distant galaxies has been mapped by scientists. Less than 2 billion years after the Big Bang, the 1.5 million galaxies appear as they did 12 billion years ago, or less than 12 billion years after the Big Bang. As observed from Earth, these galaxies distort the cosmic microwave background, which is light released during an even earlier age of the cosmos. Scientists claim that this distortion, known as gravitational lensing, exposes the distribution of dark matter around these galaxies.
Researchers may learn more about dark matter if they can figure out how it gathers around galaxies early in the universe’s existence. Additionally, in the future, this lensing technique might aid researchers in solving a conundrum regarding the clumping of matter in the universe.
Galaxies are surrounded by a mysterious, huge substance called dark matter. Although dark matter has never been directly observed by scientists, they can nevertheless see the gravitational effects it has on the universe (SN: 7/22/22). One of these effects is gravitational lensing, whereby the bulk of a galaxy bends light like a lens as it passes by. The amount of light’s bending exposes the galaxy’s mass, including its dark matter.
According to cosmologist Hironao Miyatake of Nagoya University in Japan, it is challenging to trace dark matter around such far-off galaxies. That’s because researchers require a light source that is farther remote than the galaxy serving as the lens. Usually, astronomers attribute the origin of the light to even farther away galaxies. But those galaxies are hard to find when looking thus far into space.
Miyatake and associates instead looked to the cosmic microwave background, which is the universe’s oldest source of light. In addition to numerous far-off galaxies seen by the Subaru Telescope in Hawaii, the team employed measurements of lensing of the cosmic microwave background taken by the Planck satellite (SN: 7/24/18). We require a large number of lens galaxies since the gravitational lensing effect is so negligible, claims Miyatake. According to the researchers, the distribution of dark matter surrounding the galaxies was as expected.
The amount of “clumpy” matter in the cosmos, known as sigma-8, was also estimated by the researchers. The discrepancy between various readings of sigma-8 has long been suspected by experts (SN: 8/10/20). That might be a sign that the cosmos as it is now understood by scientists is flawed. But the evidence does not prove anything.
Whether or whether that tension exists is one of cosmology’s most intriguing topics at the moment, according to Stanford University cosmologist Risa Wechsler, who was not involved in the work. This is a great good illustration of one of the methods that will assist clarify it.
Using early, far-off galaxies for sigma-8 measurement could shed light on the situation. Cosmologist Hendrik Hildebrandt of Germany’s Ruhr University Bochum, who was not involved in the work, argues that “you want to quantify this amount, this sigma-8, from as many angles as possible.”
If estimates from various periods of the universe diverge, this might aid scientists in developing a new theory that could more adequately describe the cosmos. Although the current sigma-8 assessment is not exact enough to end the controversy, upcoming initiatives like the Rubin Observatory in Chile could make the estimate more accurate (SN: 1/10/20).