Astronomers Reveal Unseen Starburst Galaxies

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Astronomers announced today that have characterized hundreds of previously unseen starburst galaxies. The starburst galaxies, which produce hundreds of stars each year, reveal that high star-formation rates have been the norm for much of our universe's history.

Using the European Space Agency's (ESA) Herschel space observatory and W.M. Keck telescopes, astronomers measured the temperature, brightness, and star formation rate of thousands of galaxies that are shrouded by vast amounts of dust.

“Starburst galaxies are the brightest galaxies in the Universe and contribute significantly to cosmic star formation, so it’s important to study them in detail and understand their properties,” said Caitlin Casey, lead author of a paper on the discovery published recently in The Astrophysical Journal and an astronomer at the University of Hawaii. "Some of the galaxies found in this new survey have star-formation rates equivalent to the birth of several thousand solar-mass stars per year, constituting some of the brightest infrared galaxies yet discovered.”

Our Milky Way Galaxy, on average, produces only one sun-like star per year. Starburst galaxies, with their exceptional star formation, would outshine the Milky Way hundreds to thousands of times over if they weren't covered in dust that absorbs much of the their visible light. Herschel was able to measure the infrared radiation emitted by the galaxies.

Researchers then used the Keck telescopes to measure the redshifts of the starburst galaxies, determining how early in time the light from each galaxy comes. Most of the galaxies are 10 billion years old or less, but around 5% were older, with some having formed only 1 billion years after the beginning of the universe.

“The Herschel data tell us how fiercely and prolifically these galaxies are producing stars,” said Seb Oliver, principal investigator for the HerMES Key Programme, into which the data have been collected. “Combining this information with the distances provided by the Keck data, we can uncover the contribution of the starburst galaxies to the total amount of stars produced across the history of the universe.”

Astronomers will use the new data to help determine how large numbers of starburst galaxies formed during the first few billions of years of the universe. Their existence complicates current hypotheses on galaxy formation and evolution.

“It’s a hotly debated topic that requires details on the shape and rotation of the galaxies before it can be resolved,” said Casey.

(Image courtesy ESA–C. Carreau/C. Casey (University of Hawaii); COSMOS field: ESA/Herschel/SPIRE/HerMES Key Programme; Hubble images: NASA, ESA)

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