Research estimates that about a quarter of the total mass of the universe is dark matter, and it is located in the "orolas" surrounding the galaxy, and information about the evolution of this invisible substance can be obtained by examining various "indirect" effects.
In a new work published in Physical Review Letters, astrophysicists used relic-radiation analysis to map the distribution of dark matter in the galaxy that existed 1.7 billion years after the Big Bang.
Gravity lens opens the invisible
Dark matter does not participate in electromagnetic interaction, which means it does not emit waves at any of the frequencies. Stars and galactic clusters, whose photos attract wide attention, can be seen in visible and infrared light.
The general theory of relativity and gravitational lensing comes in handy. It is known that massive objects distort the surrounding space and time. If there are others outside the study galaxy, the light that will pass will be distorted by gravity. Therefore, the visible form of the galaxy will be changed.
Watching the same galaxy behind the gravitational lens and outside, you can tell how much the light is distorted, the more the distortion, the larger the mass of the galaxy, and so the mass of dark matter.
This model makes reality a little easier, but it describes technology very well. In real research, it's almost impossible to find two galaxies, one of which will only be influenced by the other. Such gravitational effects can be many, and all of them must be taken into account.
8 - 10 billion light years is the limit
The gravitational lens technology based on distant galaxies is widely applied, and astrophysics has studied the distribution of dark matter in many cosmic clusters, but the further the object is, the stronger its red shift, the more difficult it is to use this technique.
The problem is that, at some point, distant galaxies become too thin, and therefore it is very difficult to trace the distortions that cause the gravitational lens. The further away from the Earth the object is needed, the less effective the technique becomes. The distortion of the lens is thin and, in most cases, difficult to detect, so many background galaxies are needed to study.
Without being able to detect long-range original galaxies to measure distortion, researchers encountered limitations; they were able to analyse only dark matter no more than 8–10 billion years ago, and other scientists came up with the same results.
How could a new study be carried out?
To collect the necessary data, scientists have explored more than 1.5 million galaxies with an average red shift of about 4. Space objects are removed from each other due to the expansion of the universe, and the frequency of electromagnetic radiation becomes smaller, for example, the visible light is moving towards the red side of the spectrum. By studying this effect, it is possible to estimate the age of remote objects. The cosmological red displacement of 4 corresponds to galaxies located at a distance of about 12 billion light years.
Because visible light emanating from more distant objects was not enough to study gravity distortions, researchers used relic radiation observations from Plank.
Relict radiation is an evenly filling of the universe's thermal radiation from the age of primary hydrogen recombination, and scientists have changed the light to microwaves and studied how gravitational lenses distort that radiation.
It was a crazy idea. No one knew we could do it, but after I gave a talk about a big set of distant galaxies, Hironao came up to me and said that it was possible to explore the dark matter around these galaxies with relic radiation.
After preliminary analysis, researchers realized that they had a large enough sample to detect the distribution of dark matter. By combining a sample of a large distant galaxy and the distortion of the lens in relic radiation, they discovered dark matter 12 billion years ago, just 1.7 billion years after the beginning of the universe, which means that these galaxies are visible shortly after formation.
What did they find out?
The most amazing discovery of researchers is associated with the combularity of dark matter. Standard cosmological theory suggests that thin fluctuations of relic radiation form clusters of heavily packed matter, drawing the surrounding substance under the influence of gravity. This creates heterogeneous clusters that form stars and galaxies in these dense areas.
The results of the new study showed that dark matter compost in the early universe was lower than the Lambda-CDM model predicted. This means that if measurements are correct, then the existing theory misstates evolution in the first billion years after the Big Bang, which means that we need to clarify the nature and development of matter and the Standard cosmological theory.
Now we're going to try to get better data to see if the Lambda-CDM model is really able to explain the observations that we have in the universe, and the consequence may be that we need to re-examine the assumptions that came into this model.
So far, scientists have studied only one third of the total amount of data received; additional processing will help to clarify the available results and the distribution of dark matter; they also plan to use data sets from other telescopes to expand research and look further, 1 billion years after the Big Bang.