March 13, 2013
Starburst Galaxies Observations Reveal They Occured Earlier In Universe Than Previously Believed
WATCH VIDEO: [Gravitational Lensing of Distant Star-Forming Galaxies]
Lee Rannals for redOrbit.com — Your Universe OnlineAstronomers reported in Nature and the Astrophysical Journal that starburst galaxies from early in the universe's history took place earlier than previously though.
Scientists making observations with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope say they have found that the most vigorous bursts of star birth in the universe actually took place earlier than previously thought. These starburst galaxies convert reservoirs of gas and dust into new stars many hundreds of times faster than in spiral galaxies like our own. Astronomers are able to see these distant galaxies by looking far into space, at light that takes billions of years to reach us.
“The more distant the galaxy, the further back in time 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 history,” said Joaquin Vieira of the California Institute of Technology (Caltech), who led the team and is lead author of the paper in the journal Nature.
The team first observed the latest distant starburst galaxies with the US National Science Foundation´s (NSF) 10-meter South Pole Telescope (SPT), and then used ALMA to zoom in and make a more detailed observation. They found that many of these distant star-forming galaxies are further away than expected, when the Universe was just under two billion years old.
Two of the galaxies observed are the most distant ever seen, one of which started emitting light when the Universe was just one billion years old. In another one of these record-breaking galaxies, astronomers said they saw the most distant observations of water in the universe ever.
“ALMA´s sensitivity and wide wavelength range mean we could make our measurements in just a few minutes per galaxy – about one hundred times faster than before,” said Axel Weiss of Max-Planck-Institut fÃ¼r Radioastronomie (MPIFR) in Bonn, Germany, who led the work to measure the distances to the galaxies. “Previously, a measurement like this would have been a laborious process of combining data from both visible-light and radio telescopes.”
The team also had to use a technique known as gravitational lensing to make the observations. This technique works when light from a distant galaxy is distorted by the gravitational influence of a nearer foreground galaxy.
"These beautiful pictures from ALMA show the background galaxies warped into multiple arcs of light known as Einstein rings, which encircle the foreground galaxies," said Yashar Hezaveh (McGill University, Montreal, Canada), who led the study of the gravitational lensing. “We are using the massive amounts of dark matter surrounding galaxies half-way across the Universe as cosmic telescopes to make even more distant galaxies appear bigger and brighter.”
An analysis of the distortion reveals that some of the distant star-forming galaxies are as bright as 40 trillion Suns.
“Only a few gravitationally lensed galaxies have been found before at these submillimetre wavelengths, but now SPT and ALMA have uncovered dozens of them.” said Carlos De Breuck, a member of the team from the European Southern Observatory (ESO). “This kind of science was previously done mostly at visible-light wavelengths with the Hubble Space Telescope, but our results show that ALMA is a very powerful new player in the field.”
Team member Daniel Marrone, from the University of Arizona, said this is just the beginning for ALMA and for the study of these starburst galaxies.
"Our next step is to study these objects in greater detail and figure out exactly how and why they are forming stars at such prodigious rates," Marrone added.
In January, the ESO announced that ALMA started a new and more advanced phase of science observations. ALMA's first scientific operations began in 2011, but the large telescope array is still under construction.
ALMA, the largest astronomical project in the world, was officially inaugurated in Chile this morning. During the day, presentations about the development of the array were made, as well as what the future of the ALMA project holds.