Sidney Fellow throws new light on star formation

The strongest burst of star formation occurred two billion years after the Big Bang according to new research led by a Fellow of the College.

Dr Scott Chapman, of the University’s Institute of Astronomy, spoke on Tuesday on new observations from some of the most distant galaxies in the Universe at the Royal Academy of Science (RAS) National Astronomy Meeting in Belfast.

His work has provided evidence for a dramatic surge in star birth within these galaxies, which have only recently been discovered and are so distant that the light we can detect from them has been travelling for 10 billion years. Accordingly, we see them as they were about three billion years after the Big Bang.They still have large reservoirs of gas, which will power star formation for several hundred million years. Supporting evidence comes from a parallel study by PhD student Caitlin Casey, who found that star formation in these galaxies is distributed over a vast area.

The rate is far higher than anything seen in the present-day Universe, and probably developed after the first stars and galaxies had already formed in what would have been a perfectly smooth Universe. Studying these new objects will give astronomers new insight into the earliest epochs of star formation after the Big Bang.The recent discovery of a new type of galaxy in this epoch is the key to the new results. The galaxies in question, although very faint in visible light, are much brighter at radio wavelengths.

A related type of galaxy was discovered in 1997 using a new, sensitive camera called SCUBA, which detects radiation at submillimetre wavelengths (longer than visible light, but shorter than radio waves).

In 2004, the Cambridge-led team suggested that the ‘submillimetre’ galaxies might only represent half of the picture, since SCUBA is intended to pick up colder objects. They suggested that a slightly hotter population of similar galaxies could have gone unnoticed.

Work to search for these galaxies was conducted by an international team of astronomers from the UK, France, Germany and the USA. Observatories around the world, including the UK’s MERLIN array, the Very Large Array and Keck optical telescope in the US, and the Plateau de Bure observatory in France were used to pinpoint them, measure their distances and confirm their star-forming nature through the detection of vastly extended gases and dust.

The new discoveries have allowed for a much more accurate census of some of the most distant galaxies at the peak of their activity. Future observations will look at the details of the galaxies' power source and try to establish how they will develop after their intense bursts of activity come to an end.

This is an archived news story, first posted in 2008.