Scientists from Japan, Europe, and the United States directly recorded extended linear structures of hydrogen that stretch between galaxies in the distant proto-cluster. Researchers previously recorded indirect evidence of such formations predicted by standard cosmological theory, but in this case, their presence manifested itself most clearly.
The modern cosmological theory ΛCDM describes most of the observed large-scale processes in the Universe. In particular, it determines the evolution of structures on a large scale and the rate of formation of clusters of galaxies. According to the results of numerical simulations carried out on its basis, matter in the Universe should form a network resembling soap foam: walls and threads with a relatively high concentration of matter, bordering on vast areas of low density – voids.
A similar structure can be traced for relatively close galaxies: they line up in filaments, called filaments, at the intersection of which are large clusters of galaxies. Since galaxies and stars are formed from hydrogen, a filamentary structure should also be traced in its distribution. However, hydrogen can be present in the form of diffuse clouds, in which there are no luminous objects, such as stars, so it is difficult to see the gas component of a large-scale structure directly.
At the same time, observing the hydrogen component of a large-scale structure is of particular value for science, since it is this gas that must flow along the filaments onto the forming galaxies and provide conditions for the rapid growth of supermassive black holes at their centers. Astronomers have already recorded the presence of this gas, but by indirect signs: either by distorting the appearance of more distant galaxies or by absorbing the radiation of bright quasars in the background.
The work of astronomers, led by Hideki Umehata from the Japan Institute of Physico-Chemical Research RIKEN, describes the detection of hydrogen filaments in the distant proto-cluster of SSA22 galaxies at a redshift of 3.1. Scientists were able to fix the ultraviolet (in the resting frame of reference) gas glow from several oblong gas structures that stretch between galaxies at a distance of more than one megaparsec.
The light from this cluster has been going on for a long time, we see it as it was only about two billion years after the Big Bang. At this time, the active formation of galaxies and their clusters, as well as the growth of supermassive black holes, just continued. The authors of the article believe that it was intense star formation and activity of large black holes that excited hydrogen in the filaments, which then began to glow in the Ly α line, which corresponds to the transition of an electron from the first excited level to the ground.
Numerical models show that at that time at least 60 percent of all gas in the Universe should have been in the form of filaments. The authors call the results of their work the first full-fledged detection of filaments connecting several galaxies, since earlier it was only possible to deduce their presence in several special cases. Achievement was made possible thanks to the MUSE spectrometer mounted on the VLT eight-meter telescopes in Chile.
The work is also important in the context of the “lost baryons” problem – the apparent lack of ordinary matter in the local Universe. The cosmological ΛCDM model predicts that there should be more of the best known component of the Universe around us, but it was not possible to fix it in observations. In some works, successful registration of hydrogen in the form of hot gas in the bridges between the galaxies – the evolved filaments from the early Universe was mentioned.
Previously, astrophysicists were able to determine the shape of the Local Void, found a standard ruler for the era of universal dawn, and measured the expansion of the universe using the size of gravitational lenses.
Via | the Journal Science