UTexas: Hubble Finds Faintest Early Galaxies Yet

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UTexas: Hubble Finds Faintest Early Galaxies Yet

Post by bystander » Wed Feb 08, 2017 6:33 pm

Astronomers Find Faintest Early Galaxies Yet,
Probe How the Early Universe Lit Up with HST

McDonald Observatory | University of Texas, Austin | 2017 Feb 08
[img3="Galaxy Cluster MACS 0416"]https://mcdonaldobservatory.org/sites/d ... k=q7IIg2e8[/img3] [img3="Galaxy Cluster Abell 2744
Credit: STScI/NASA/CATS Team/R. Livermore (UT Austin)

Cyan highlights the distribution of mass in the clusters, mostly in the form of dark matter. Magenta highlights the degree to which the background galaxies are magnified, which is related to the mass distribution."]https://mcdonaldobservatory.org/sites/d ... k=EPQ59iwi[/img3][hr][/hr]
Astronomers at the University of Texas at Austin have developed a new technique to discover the faintest galaxies yet seen in the early universe -- 10 times fainter than any previously seen. These galaxies will help astronomers probe a little-understood, but important period in cosmic history. Their new technique helps probe the time a billion years after the Big Bang, when the early, dark universe was flooded with light from the first galaxies.

Rachael Livermore and Steven Finkelstein of UT Austin, along with Jennifer Lotz of the Space Telescope Science Institute, went looking for these faint galaxies in images from Hubble Space Telescope’s Frontier Fields survey.

“These galaxies are actually extremely common,” Livermore said. “It’s very satisfying being able to find them.”

These faint, early galaxies gave rise to the epoch of reionization, when the energetic radiation they gave off bombarded the gas between all galaxies in the universe. This caused the atoms in this diffuse gas to lose their electrons (that is, become ionized).

Finkelstein explained why finding these faint galaxies is so important. “We knew ahead of time that for our idea of galaxy-powered reionization to work, there had to be galaxies a hundred times fainter than we could see with Hubble,” he said, “and they had to be really, really common.” This was why the Hubble Frontier Fields program was created, he said.

Lotz leads the Hubble Frontier Fields project, one of the telescope’s largest to date. In it, Hubble photographed several large galaxy clusters. These were selected to take advantage of their enormous mass which causes a useful optical effect, predicted by Albert Einstein. A galaxy cluster’s immense gravity bends space, which magnifies light from more-distant galaxies behind it as that light travels toward the telescope. Thus the galaxy cluster acts as a magnifying glass, or a “gravitational lens,” allowing astronomers to see those more-distant galaxies -- ones they would not normally be able to detect, even with Hubble.

Even then, though, the lensed galaxies were still just at the cusp of what Hubble could detect. ...

Directly Observing the Galaxies Likely Responsible for Reionization - R.C. Livermore, S.L. Finkelstein, J.M. Lotz
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