Spotting Distant Galaxy Clusters With WISE
December 7, 2012

WISE Telescope Spies Gigantic Galaxy Clusters

April Flowers for - Your Universe Online

As grand and colorful as it is, our solar system is a fleck in the grander cosmos. Our Milky Way galaxy has hundreds of billions of solar systems, yet it is only just a drop in the sea of galaxies.

Galaxy clusters, the rarest and largest of galaxy groupings, can be the hardest to find, which is where NASA's Wide-field Infrared Survey Explorer (WISE) becomes helpful. So far, the mission's all-sky infrared maps have revealed one distant galaxy cluster and are expected to uncover thousands more.

A galaxy cluster is a collection of up to thousands of galaxies bound together by gravity. The cluster was born out of seeds of matter formed in the very early universe and experienced rapid growth from a process called inflation.

"One of the key questions in cosmology is how did the first bumps and wiggles in the distribution of matter in our universe rapidly evolve into the massive structures of galaxies we see today," said Anthony Gonzalez of University of Florida, Gainesville. "By uncovering the most massive of galaxy clusters billions of light-years away with WISE, we can test theories of the universe's early inflation period."

In 2011, WISE completed its all-sky survey after surveying the entire sky twice at infrared wavelengths. As expected, the 16-inch telescope ran out of coolant in 2010. However, it was able to complete the second sky scan using two of its four infrared channels that functioned without coolant. The goal of WISE's mission extension was to hunt for more near-Earth asteroids via a project called NEOWISE.

The WISE team has since combined all the data, allowing astronomers to study everything from nearby stars to distant galaxies. Significantly more sensitive than those previously released, these next generation all-sky images are part of a new project called "AIIWISE." The images will be made publically available in late 2013.

The team plans to look for more massive galaxy clusters using the enhanced WISE data. The one they have spotted so far, MOO J2342.0+1301, is located about 7 billion light-years away. This puts it about halfway back to the time of the Big Bang. This galaxy cluster is hundreds of times more massive than our own Milky Way.

Using the improved AIIWISE data to scan the entire sky, the team will search out the true monsters of the bunch. These clusters are expected to be thousands of times larger than the Milky Way and even farther back in the history of the universe than MOO J2342.0+1301.

Because they are so far away and not many had time to assemble by then, galaxy clusters from the early universe are hard to find. Moreover, they are difficult to see using visible-light telescopes. The light that left these faraway structures in visible wavelengths has been stretched into longer, infrared wavelengths because of the expansion of space. Because WISE scanned the entire sky in infrared, it is capable of hunting down some of these rare colossal structures.

"I had pretty much written off using WISE to find distant galaxy clusters because we had to reduce the telescope diameter to only 16 inches to stay within our cost guidelines, so I am thrilled that we can find them after all," said Peter Eisenhardt, the WISE project scientist at NASA's Jet Propulsion Laboratory. "The longer exposures from AllWISE open the door wide to see the most massive structures forming in the distant universe."

Other projects are planned for the WISE enhanced data include the search for nearby cool stars — some with masses as low as planets — called a "Tyche." If such a celestial object exists close to our solar system, WISE will reveal it in the infrared data.

The results of this study were published in the Astrophysical Journal.