The grouping of hundreds or thousands of galaxies originate aggregates called clusters, whose center is occupied by the giant galaxies.
“We thought that, in the initial stages of the universe, these huge galaxies were formed from other small ones that merged with each other under the action of their own gravity, as happens in the next universe, but we have seen that everything is much more complicated ”, says Bjorn Emonts, researcher at the Center for Astrobiology (INTA / CSIC).
He is the lead author of a study, published this week by Science, which opens up a new avenue to study how giant galaxies formed in the early universe.
The authors have studied a cluster located 10 billion light-years from Earth using the ATCA (Australia Telescope Compact Array) radio telescope array in Australia and the VLA (Very Large Array) in the United States.
In the center of this cluster is MRC 1138-262, nicknamed Spiderweb (Cobweb, for its appearance), a super galaxy that is forming immersed in a huge cloud of cold gas.
"This cosmic ocean contains approximately 100,000 million times the mass of the Sun and is composed mostly of hydrogen molecules, the raw material from which stars and galaxies are formed," says Montserrat Villar-Martín, also a CAB scientist and co-author from work.
But instead of looking at hydrogen directly, the researchers have detected it through a tracer gas - in this case, carbon monoxide - that is easier to locate.
"We expected to detect the cold gas in the merging galaxies," says co-author Helmut Dannerbauer, from the Instituto de Astrofísica de Canarias (IAC), who, in 2014, revealed that Spiderweb is surrounded by a large number of galaxies hidden behind thick layers of dust.
The observations revealed, instead, that most of the cold gas is not there, but occupies the vast space between galaxies. Astronomers now think that the supergalaxy originated directly from the condensation of that cosmic ocean of cold gas.
And if this can happen in this case, it could also happen in other giant galaxies, in addition to suggesting that the formation of galaxies in the early universe is a process that is quite different from that studied in the closest universe.
The mystery of cold gas
“We now know how and where to look for the giant reservoirs of cold gas that make up the largest galaxies in the universe. From this moment on, we will be able to use the most advanced astronomical technology to find similar systems ”, adds Villar-Martín. Where the cold gas comes from is still a puzzle for the scientific community.
“The carbon monoxide that we detect is a by-product of now-disappeared stars, a form of cosmic recycling, but we cannot be sure of the origin of the gas or how it accumulates in the core of the cluster”, explains Emonts, who advances: “To To find out, we will have to delve even deeper into the history of the universe. "