Explosion Of Galaxy Growth In The Early Universe

September 7, 2012
Image Caption: The South Pole Telescope stands 75 feet tall in Antarctica’s clear, dry air. Members of the SPT collaboration have published two papers in the Astrophysical Journal presenting evidence that the first stars and galaxies formed more rapidly than previously believed. Credit: Keith Vanderlinde

April Flowers for redOrbit.com – Your Universe Online

A new study from the University of California, Berkeley indicates that the birth of the first massive galaxies that lit up the early universe was an explosive event, happening faster and ending sooner than suspected.

Around 13 billion years ago, when the universe was about 750 million years old, extremely bright, active galaxies formed and fully illuminated the universe, according to Oliver Zahn, a postdoctoral fellow at the Berkeley Center for Cosmological Physics (BCCP) at the University of California, Berkeley, who led the data analysis.

This new data, from the South Pole Telescope, provides new constraints on the universe’s first era of galaxy formation, called the Epoch of Reionization. Early stars came to life in massive gas clouds, generating the first galaxies, so most astronomers think. The energetic light pumped out by these stars is thought to have ionized the hydrogen gas in and around the galaxies. This created “ionization bubbles” millions of light years across leaving a lasting, telltale signature in the cosmic background radiation (CMB). This relic light from the early universe is visible today everywhere in the sky and was first mapped by UC Berkeley physicist and Nobel laureate George Smoot, founder of the BCCP.


Just after the Big Bang, everything was so hot that all the gas, mostly hydrogen, was ionized during the first epoch of ionization. The universe only cooled enough for electrons to latch onto protons to form neutral hydrogen atoms when the universe was about 400,000 years old.


The short duration of this epoch suggests that monster galaxies with more than a billion stars played a key role in the reionization, since smaller galaxies would have formed much earlier.

The results of the study, a collaboration between UC Berkeley and the University of Chicago, are published in the September 1 edition of The Astrophysical Journal.

The results are based on a new analysis that combines measurements taken by the South Pole Telescope at three frequencies and extends the measurements to a larger area covering approximately 2 percent of the sky. The 75-foot-tall South Pole Telescope, located at the Amundsen Scott South Pole station in Antarctica, operates at millimeter wavelengths to make high-resolution images of the CMB and its polarization.

The team combined this new data with earlier data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite and was able to put stringent constraints on when the epoch or reionization began and how long it lasted.

WMAP is a NASA Explorer mission launched to make fundamental measurements of cosmology — the study of our universe as a whole. Though WMAP’s transmission has ended, analysis of the data is still ongoing.


Astronomers were unsure whether they would be able to constrain the Epoch of Reionization using the CMB because of uncertainty over how stars formed, clustered and spewed ionizing radiation into the interstellar medium in the early universe. Over the past decade, however, various groups developed models of these processes. Zahn and his team used them to work backwards to put limits on when the era began and ended.


Astronomers expect to learn a great deal more from the South Pole Telescope. The current results are based on only the first third of the full telescope survey. Additional work is underway to combine the telescope’s maps with ones made with the Herschel satellite to further increase the sensitivity to the reionization signal.

“We expect to measure the duration of reionization to less than 50 million years with the current survey,” Christian Reichardt, University of Chicago, said. “With planned upgrades to the instrument, we hope to improve this even further in the next five years.”


Source: April Flowers for redOrbit.com - Your Universe Online

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