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Giant galaxies are born in cosmic clouds of cold gas

Giant galaxies are born in cosmic clouds of cold gas

Washington: Scientists using radio telescopes in Australia and the USA discovered that the biggest galaxies in the universe develop in cosmic clouds of cold gas.

Findings were published in the journal Science.

Until now scientists believed that these “supergalaxies” formed from smaller galaxies that grow closer and closer together until they merge, due to gravitational attraction.

Galaxies are usually grouped into clusters, huge systems comprising up to thousands of millions of these objects, in whose interior are found the most massive galaxies in the universe.

“In the local universe, we see galaxies merging and expected to observe that the formation of supergalaxies took place in the same way, in the early (now distant) universe,” said first author Bjorn Emonts from Centro de Astrobiología (CSIC-INTA) in Madrid.

To investigate this, telescopes were pointed towards an embryonic galaxy cluster 10 thousand million light years away, in whose interior the giant Spiderweb galaxy is forming and discovered a cloud of very cold gas where the galaxies were merging.

This enormous cloud, with some 100 thousand million times the mass of the Sun, is mainly composed of molecular hydrogen, the basic material from which the stars and the galaxies are formed.

Instead of observing the hydrogen directly, they did so using carbon monoxide, a tracer gas which is much easier to detect. “It is surprising”, comments Matthew Lehnert, second author of the article and researcher at the Astrophysics Institute of Paris, “how cold this gas is, at some 200 degrees below zero Celsius. We would have expected a lot of collapsing galaxies, which would have heated the gas, and for that reason we thought that the carbon monoxide would be much more difficult to detect”.

However, combining the interferometers VLA (Very Large Array) in New Mexico ( USA) and the ATCA (Australia Telescope Compact Array) in Australia, they could observe and found that the major fraction of the carbon monoxide was not in the small galaxies.

“We can see only the gas in the central galaxy, which is one third of all the carbon monoxide detected with the ATCA. This latter instrument, which is more sensitive for observing large structures, revealed an area of size 70 kiloparsecs (some 200,000 light years) with carbon monoxide distributed around the big galaxy, in the volume populated by its smaller neighbors. Thanks to the two interferometers, we discovered the cloud of cosmic gas entangled among them,” explained another author Helmut Dannerbauer. (ANI)