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Extragalactic survey

09 April 2009

BLAST ready for launch in AntarcticaBLAST ready for launch in Antarctica

An international team of scientists involving Cardiff University has released the first detailed colour images showing that half of the universe's starlight comes from young stars in distant galaxies.

Physicists, including a team led by Dr Enzo Pascale of the School of Physics and Astronomy, spent two years analysing data collected using the Balloon-borne Large-Aperture Sub-millimeter Telescope (BLAST). The telescope was flown attached to a stratospheric helium balloon in 2006, 35km above Antarctica.

In the late 1990’s, certain galaxies called Ultra-luminous Infrared Galaxies were found to be forming stars at a rate hundreds of times more than our own galaxy. These ''starburst'' galaxies, 7-10 billion light years away, were thought to make up the Far Infrared Background, an almost uniform radiation glowing everywhere in the universe. Since the initial measurement of this background radiation, experiments have tried to detect the individual galaxies that comprise it.

BLAST soon after launch on its climb to the top of the stratosphereBLAST soon after launch on its climb to the top of the stratosphere

The study, published in the current issue of Nature, has uncovered a population of dust-enshrouded galaxies hiding about half of the cosmic starlight, essentially solving the decade-old question of the radiation’s origin. It combines the telescope survey measurements with data from the Spitzer Space Telescope, and confirms that all the Far Infrared Background comes from individual dusty galaxies.

The released BLAST images reveal a young universe, much different than it is today, with young galaxies breeding stars at a very high rate, and generating most of the stellar masses observed today. As much as 50 percent of the universe's light energy is released as infrared light from these young forming galaxies. In fact, there is as much energy in the Far Infrared Background as there is in the total optical light emitted by stars and galaxies in the universe.

"In one epic 11-day balloon flight, BLAST found more than 10 times the total number of submillimetre starburst galaxies detected in a decade of ground-based observations", said Dr Enzo Pascale who led the Cardiff team. "This rich data collected is being mined for further information about the dust-enshrouded galaxies, to give a better understanding of their evolutionary history, their relationship with other galaxies, and associations with larger-scale structures in the universe".

BLAST image of the distant universe. Each white spot, circled in yellow, is the glowing thermal light from galaxies undergoing episodes of massive star formation

BLAST image of the distant universe. Each white spot, circled in yellow, is the glowing thermal light from galaxies undergoing episodes of massive star formationBLAST image of the distant universe. Each white spot, circled in yellow, is the glowing thermal light from galaxies undergoing episodes of massive star formation

The extragalactic survey provides new cosmological limits on the abundance and brightness of starburst galaxies, and can be used to answer fundamental questions about how and when galaxies formed, which are ultimately related to the existence of humankind.

BLAST is an instrument that can determine the temperature and brightness of distant galaxies and give an estimate of the rate of star formation. The dramatic journey from its first flight in the Arctic to the second flight in Antarctica was the subject of a feature-length documentary film, "BLAST!" which premièred in Wales at Cardiff University, and was also shown on BBC.

As part of a series of companion papers, the BLAST collaboration is also releasing the results of a study (submitted to the Astrophysical Journal) from the largest survey to date of the earliest stages of star formation. The study has documented the existence of a large population of cold clouds of gas and dust, which exist for millions of years, and eventually form the birthplace of stars.

Images, photographs, sky maps and the complete study are available at the BLAST web-site: http://www.blastexperiment.info .

The BLAST team, in addition to Cardiff University, involves Brown University, the Universities of Pennsylvania, Toronto, Puerto Rico, Miami, and British Columbia, the Jet Propulsion Laboratory, and Laboratoire APC in Paris.

The research was supported by the Science and Technology Facilities Council in the UK, and the Cardiff team included: Professor Peter Ade, Professor Matthew Griffin, Dr Peter Hargrave, Professor Philip Mauskopf, Lorenzo Moncelsi, Dr Enzo Pascale and Dr Carole Tucker, all members of the School’s Astronomy Instrumentation Group.

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