Astronomers have known for some time that the earliest galaxies were much smaller than the impressive spiral and elliptical galaxies that now fill the Universe. Over the lifetime of the cosmos galaxies have put on a great deal of weight but their food, and eating habits, are still mysterious. A new survey of carefully selected galaxies has focussed on their teenage years — roughly the period from about 3 to 5 billion years after the Big Bang. By employing the state-of-the-art instruments on ESO’s Very Large Telescope an international team is unravelling what really happened. In more than one hundred hours of observations the team has collected the biggest ever set of detailed observations of gas-rich galaxies at this early stage of their development.

The new results point toward a big change in the cosmic evolution of galaxies, when the Universe was between 3 and 5 billion years old. Smooth gas flow seems to have been a big factor in the building of galaxies in the very young Universe, whereas mergers became more important later.

"What we have found is a correlation between stellar mass and the galaxies' recession speeds. This correlation is already known in the local universe, but we demonstrated to be present since 8 billion years ago, even with a higher dispersion" says Daniela Vergani, researcher at INAF-IASF in Bologna, who participated in the discovery. "We believe that the disperion is intrinsic, and that is caused by complex mechanisms acting during the cosmic age when galaxies were adolescent: an extreme turbulent period for them".

For more information visit ESO Website