Observations with the Atacama Large Millimeter/submillimeter Array (ALMA), an array of 66 radio telescopes located in the dry and cloudless Atacama Desert in Chile, show that the most vigorous bursts of star birth took place much earlier than previously thought.

The most intense bursts of starbirth are thought to have taken place in the early Universe in massive, bright galaxies containing lots of cosmic dust. By looking far into space, at galaxies which are so distant that their light has taken many billions of years to reach us, astronomers can observe this busy period of the Universe’s youth.

An international team of astronomers used data gathered from the South Pole Telescope to select a sample of 26 potentially lensed, dusty starburst galaxies and then used ALMA to obtain both imaging and spectroscopy.

The imaging data demonstrated that these sources are strongly lensed by foreground galaxies, which increases their apparent luminosities by a factor of ~10, which translates to a savings in telescope time of ~100, and allows such distant and intrinsically faint objects to be more easily detected. The spectroscopic observations provided redshifts for the sources and information on their gas content.

From these observations, the astronomers were able to roughly double the number of known starburst galaxies that exist in the so-called high-redshift Universe.

Two of the galaxies are at a redshift of 5.7. They are the most distant of their kind ever seen – so distant that their light began its journey when the Universe was only 1 billion years old. What’s more, in one of these record-breakers, water is among the molecules detected, marking the most distant observations of water in the cosmos published to date.

The results appear in a paper published in the journal Nature (ESO’s version), and two papers accepted for publication in the Astrophysical Journal (paper 2 & paper 3).

“The more distant the galaxy, the further back one is looking, so by measuring their distances we can piece together a timeline of how vigorously the Universe was making new stars at different stages of its 13.7 billion year life,” said Dr Joaquin Vieira of the California Institute of Technology, lead author of the Nature paper.

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Bibliographic information: J. D. Vieira et al. Dusty starburst galaxies in the early Universe as revealed by gravitational lensing. Nature, published online March 13, 2013; doi: 10.1038/nature12001

Weiss et al. ALMA redshifts of millimeter-selected galaxies from the SPT survey: The redshift distribution of dusty star-forming galaxies. Accepted for publication in the Astrophysical Journal; arXiv: 1303.2726

Y. Hezaveh et al. ALMA observations of strongly lensed dusty star-forming galaxies. Accepted for publication in the Astrophysics Journal; arXiv: 1303.2722