Colliding galaxies in radio wavelengths.Credit: Caitlin M. Casey (Cambridge, IoA) et al.
The strongest burst of star formation in the history of the Universe occurred about two billion years after the Big Bang, say astronomers presenting their research at the National Astronomy Meeting this week.
The international team of astronomers from the UK, France, Germany and the USA found evidence for a massive surge in star birth in a newly discovered population of massive galaxies in the early Universe. Dr Scott Chapman, from the Institute of Astronomy at Cambridge, reveals that five of the galaxies are forming stars at a tremendous rate and have large reservoirs of gas that will power the star formation for hundreds of millions of years.
The galaxies are so distant that the light we detect from them has been travelling for more than 10 billion years, meaning that we see them as they were about three billion years after the Big Bang. The recent discovery of a new type of luminous galaxy in this epoch - one that is very faint in visible light but much brighter at longer radio wavelengths - is pivotal to the new results.
A related type of galaxy was found over ten years ago using the SCUBA camera on the James Clerk Maxwell Telescope in Hawaii that detects radiation emitted at sub-millimetre wavelengths, which are longer than the wavelengths of visible light and shorter than radio waves. The SCUBA camera is biased towards cooler objects so the Cambridge-led team of astronomers concluded that these distant "submillimetre galaxies" might only represent half the picture of rapid star formation. The team proposed that a population of similar galaxies with slightly hotter temperatures could exist but had previously gone unnoticed.
Using observatories around the world, including MERLIN in the UK, the Very Large Array in the US, the Keck telescope in Hawaii and the Plateau de Bure submillimetre observatory in France, the new research team implemented a missing galaxy search, and were rewarded with the location of the galaxies exhibiting unprecedented rates of star formation, which were confirmed by the detection of vastly extended gas and dust regions around the galaxies. The researchers commented that these galaxies probably formed after the first stars and galaxies had already formed in what would have been a perfectly smooth Universe.
The new results offer a window into the earliest epochs of star formation after the Big Bang and have provided astronomers with a much more detailed census of the most active galaxies in the young Universe. Future observations will investigate further the details of the galaxies' power source and try to establish how they will develop once their intense bursts of activity come to an end.
