(ORDO NEWS) — An international team of astronomers has found evidence of a massive cluster of young galaxies, most of which are now “dead”, in the Keck Observatory data.
This is the first time astronomers have observed such an unusual phenomenon, and perhaps it will force us to reconsider the models for the formation of galaxy clusters in the early Universe.
A cluster of galaxies is a system usually consisting of dozens of relatively closely spaced and gravitationally bound galaxies. Gradually, clusters grow, capturing more and more galaxies under the influence of gravity. In this regard, clusters consisting of hundreds and even thousands of galaxies can exist in the modern Universe.
The clusters of galaxies in the early Universe (also called protoclusters) that we can observe to this day consist mainly of actively star-forming galaxies. Over time, some protocluster galaxies run out of gas from which stars are formed, and they turn into so-called dead galaxies.
“In the early universe, all the protoclusters discovered so far are full of actively star-forming galaxies,” said Ian McConachie , a graduate student in the Department of Physics and Astronomy at the University of California at Riverside and lead author of the study.
“But the incredible thing is that, unlike all other protoclusters that have been discovered during this epoch, many of the galaxies in MAGAZ3NE J0959 appear to have stopped forming stars.”
In their work, the authors describe the protocluster MAGAZ3NE J095924+022537, consisting of at least 38 galaxies and located at a distance of about 11.8 billion light years from us: this means that we see this cluster at a time when the Universe was no more than two billion years old.
Nevertheless, the proportion of resting (or dead) galaxies in the studied protocluster is about 73%. At the same time, for clusters of approximately the same age and mass, this figure does not exceed 12% on average.
“At the center of MAGAZ3NE J0959 is a supermassive galaxy that has already gained a mass of over 200 billion solar masses.
Why this supermassive galaxy and so many of its neighbors formed most of their stars and then became inactive when the universe was still so young, unlike other known protoclusters of the same time, is a big mystery, ”adds study co-author Benjamin Forrest (Benjamin Forrest of the University of California, Davis.
The protocluster MAGAZ3NE J0959 was discovered from Earth during the survey of the Keck Observatory under the acronym MAGAZ3NE – “Massive ancient galaxies with Z > 3 in the near infrared region of the spectrum”, designed to detect and study supermassive galaxies and their neighbors.
As scientists note, the emergence of powerful new space telescopes – like the recently launched James Webb Telescope – should soon show whether there are other protoclusters similar to MAGAZ3NE J0959 waiting to be discovered in the early Universe.
“If such clusters of galaxies are found in large numbers, the current paradigm of the formation of protoclusters will require a major revision.
It is necessary to develop a new model for the formation of protoclusters that exist in various states in the early Universe.
If many of the galaxies inhabiting such protoclusters do die out during the first two billion years, this will almost certainly pose serious problems for current models of galaxy formation, ”concluded Forrest.
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