For the first time, dark matter from twelve billion years ago has been detected.

For the first time, dark matter from twelve billion years ago has been detected.

A group of scientists from Nagoya College in Japan has collaborated to investigate the dark matter surrounding galaxies as they appeared twelve billion years ago, which is billions of years further back in time than ever explored before. The results they published in Physical Review Letters suggest an intriguing chance that the basic principles of the study of the universe’s origins could be dissimilar when studying its early history.

Their research, which was published in Physical Review Letters, suggests the intriguing possibility that the fundamental principles of cosmology could vary when investigating the early stages of our universe.

Seeing something that occurred such a long time ago is difficult. Because of the limited speed of light, distant galaxies appear not as they are today but as they were billions of years back. However, it is even more challenging to observe dark matter, which does not produce light.

Think about a remote source galaxy that is situated at a greater distance than the galaxy being studied to examine its dark matter. The theory of general relativity by Einstein predicts that the gravitational force of a foreground galaxy, along with its dark matter, distorts the surrounding space and time. As light from the source galaxy passes through the distortion, it curves and alters the apparent shape of the galaxy. The extent of the distortion is determined by the amount of dark matter present. Based on the distortion caused by the gravitational pull of the foreground galaxy, including its dark matter, scientists can determine the amount of dark matter present around the lens galaxy.

However, beyond a certain point, scientists encounter an issue. The galaxies located in the farthest regions of the universe are extremely dim. As an outcome, the further away from Earth we observe, the less effective this technique becomes. In the majority of instances, the distortion caused by lensing is inconspicuous and hard to detect, hence requiring numerous background galaxies to identify the signal.

Most previous research has stayed stuck at the same limits. Since they couldn’t detect an adequate number of far-off source galaxies to determine the distortion, their analysis of the dark matter was limited to a period no more than 8 to 10 billion years ago.

As a result of these constraints, it remained unclear how dark matter was distributed between the current epoch and 13.7 billion years ago, which is close to the birth of the universe.

Hironao Miyatake from Nagoya College, along with the University of Tokyo, the National Astronomical Observatory of Japan, and Princeton College, led a study group that employed microwaves emitted from the Big Bang as an alternative source of background light to overcome these challenges and observe dark matter in the farthest regions of the universe.

Initially, using data from the Subaru Hyper Suprime-Cam Survey (HSC) observations, the group determined 1.5 million lens galaxies utilizing visible light, selected to be seen twelve billion yrs earlier.

To address the lack of galaxy light from even more distant regions, the group utilized microwaves from the cosmic microwave background (CMB), the remnant radiation from the Big Bang. They measured how the dark matter surrounding the lens galaxies affected the microwaves by using data gathered by the Planck satellite of the European Space Agency.

Look at dark matter around distant galaxies.

Professor Masami Ouchi, who conducted a significant portion of the observations, was asked for their input. “It was a crazy idea. No one recognized we might do this. However, after I discussed a vast sample of distant galaxies, Hironao approached me and suggested that it might be feasible to examine the dark matter surrounding these galaxies using the cosmic microwave background (CMB).”

“Assistant Professor Yuichi Harikane from the Institute for Cosmic Ray Research at the University of Tokyo explained, “Typically, scientists rely on source galaxies to assess the distribution of dark matter from the current time to eight billion years ago. However, our utilization of the more distant CMB enabled us to observe further back into the past and measure dark matter.”. We were determining dark matter from almost the universe’s earliest moments for the first time.”

Upon conducting an initial examination, the researchers quickly realized that they had a sufficiently large sample to uncover the distribution of dark matter. By combining the vast sample of far-off galaxies and the lensing distortions in the CMB, they were able to identify dark matter from as far back as twelve billion years ago. This corresponds to a mere 1.7 billion years after the inception of the universe, which means that these galaxies are observed shortly after their formation.

Miyatake expressed his contentment with the outcomes, saying, “I am thrilled that we have uncovered a fresh outlook on that epoch. Twelve billion years ago, things were considerably different.” At that time, more galaxies were forming than today, and the first galaxy clusters were emerging. Galaxy clusters, which consist of 100 to 1000 galaxies held together by gravity and containing significant amounts of dark matter, were described by Neta Bahcall, Eugene Higgins Professor of Astronomy, professor of astrophysical sciences, and director of undergraduate research studies at Princeton College. Neta Bahcall, Eugene Higgins Professor of Astronomy, professor of astrophysical sciences, and director of undergraduate research studies at Princeton College, added that the results of the study provide a consistent understanding of galaxies and their development, as well as the distribution of dark matter within and around galaxies, and how this evolves.”

Is dark matter clumpy? 

The researchers made a remarkable discovery related to the uneven distribution of dark matter. According to the standard cosmological model Lambda-CDM, small fluctuations in the CMB cause matter to accumulate in certain areas due to gravity, resulting in clumps that give rise to stars and galaxies. However, the team’s measurements suggest that the degree of clumpiness was lower than what was predicted by the Lambda-CDM model.

Miyatake is enthusiastic about the possibilities. “Our findings are still uncertain,” he stated. A flaw in the entire model may be indicated if this finding is accurate and as we look back further in time. This is exciting because if the outcome holds after the uncertainties are lowered, it could recommend an improvement of the model that might give insight into the nature of dark matter itself.”

Andrés Plazas Malagón, a research scholar at Princeton University, stated that they would attempt to obtain more accurate information to determine if the Lambda-CDM model can truly explain the observations in the universe. The researcher commented that if the finding is correct, it would suggest that there are flaws in the entire model as we look back in time. This might require a revision of the assumptions used in the model. Additionally, one of the benefits of using large-scale surveys, such as the one used in this study, is that it allows scientists to study everything visible in the images, from nearby asteroids in our solar system to the earliest galaxies in the universe.

Michael Strauss, who is a professor and also serves as the chair of the Department of Astrophysical Sciences at Princeton College, said that the same data can be used to investigate numerous new inquiries.

This study used information available from existing telescopes, including Planck and also Subaru. The team has only reviewed a 3rd of the Subaru Hyper Suprime-Cam Survey information. The following step will be to examine the entire information set, which should enable a more precise measurement of the dark matter circulation. In the future, the group expects to use an advanced data set like the Vera C. Rubin Observatory’s Legacy Study of Space also Time (LSST) to explore more of the earliest parts of space. “LSST will enable us to observe half the sky,” Harikane stated. “I can’t think of any reason why we wouldn’t be able to observe the distribution of dark matter 13 billion years ago.”

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