This comparison shows how ZFOURGE's deep imaging at near-infrared wavelengths reveals galaxies that are practically invisible at optical wavelengths. (Credit: ZFOURGE Collaboration.)


In one of the most sensitive measurements to date, an international team of astronomers has charted the rise and fall of galaxies across 90 percent of cosmic history in the FourStar Galaxy Evolution Survey (ZFOURGE), the complete results of which were publically unveiled today (August 30) for the first time.

Texas A&M University astronomers Dr. Casey Papovich, Dr. Ryan Quadri and Dr. Kim-Vy Tran are leaders of the multi-institution, National Science Foundation-funded global effort to examine galactic clusters and the secrets behind galaxy formation and evolution using the FourStar infrared imager mounted on the 6.5-meter Magellan Telescope in Chile.

Based on images taken during a 45-night sequence from 2010 to 2012, ZFOURGE has measured distances and brightnesses to more than 60,000 galaxies spanning more than 12 billion years of cosmic time. By building a multi-colored photo album of galaxies as they grow from their faint beginnings into mature and majestic giants, ZFOURGE reveals how diverse galaxies can be.

See an animation that shows how ZFOURGE builds a colorful photo album of galaxies by combining imaging taken at optical and near-infrared wavelengths. By staring at these patches of the sky for 45 nights, ZFOURGE measures distances to more than 60,000 galaxies spanning more than 12 billion years of cosmic time.

"Perhaps the most surprising result is that galaxies in the young universe appear as diverse as they are today," said Dr. Caroline Straatman, a recent graduate of Leiden University and lead author of the survey's main paper posted to arXiv and set to be published in The Astrophysical Journal, marking the survey's completion and the official public release of the related dataset. "The fact that we see young galaxies in the distant universe that have already shut down star formation is remarkable."

Using a new set of filters sensitive to infrared light and the unprecedented precision of the FourStar camera built by ZFOURGE collaborators at Carnegie Observatories, the team was able to peer deeply into the distant universe and make a 3-D map by collecting light from more than 60,000 galaxies and measuring how far they are from our own Milky Way galaxy.

"ZFOURGE has given us the best view yet of what our own Milky Way was like in the past," Papovich said. "Ten billion years ago, galaxies like our Milky Way were much, much smaller, but they were forming stars 30 times faster than they are today."

The deep 3-D map also revealed young galaxies that existed 12.5 billion years ago where current technologies have only found a handful of such galaxies.

"The ZFOURGE measurements are really very useful, because future challenges will be to learn more about these earliest days of the universe," said Leiden astronomer and co-author Dr. Ivo Labbe. "ZFOURGE is paving the way for future studies with the James Webb Space Telescope."

ZFOURGE is also full of surprises. In the first images taken in the study, the team found one of the earliest examples of a galaxy cluster -- a 'galaxy city' made up of a dense concentration of galaxies at a time when the universe was only three billion years old.

"This finding is much like discovering an ancient city that existed earlier than any other known city," said co-author Dr. Lee Spitler from Macquarie University in Sydney.

"ZFOURGE is providing us with a highly complete and reliable census of the evolving galaxy population," added Quadri, Mitchell Astronomy Fellow within the Texas A&M George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy. "It is already helping us to address questions like, how did galaxies grow with time? When did they form their stars and develop into the spectacular structures that we see in the present-day universe?"

In addition to the Magellan telescope at Las Campanas Observatories, ZFOURGE involved data collected by many of the world's most powerful observatories, including the Hubble Space Telescope, the Very Large Telescope, the Spitzer Space Telescope, and the Herschel Space Observatory.

"ZFOURGE is a unique and powerful study that we are now releasing to the community," Tran said. "There is so much more amazing science to be done with ZFOURGE that we know it will be of lasting legacy value."

The international ZFOURGE collaboration is composed of several universities, including Leiden University in Holland, Swinburne and Macquarie in Australia, Carnegie Observatories in Pasadena, Calif. and Texas A&M, which currently hosts the survey's website and data.

To learn more about ZFOURGE and see a list of collaborators along with the complete data set, visit http://zfourge.tamu.edu.

For additional information about Texas A&M astronomy, go to http://astronomy.tamu.edu.

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Contact: Shana K. Hutchins, (979) 862-1237 or shutchins@science.tamu.edu; Dr. Kim-Vy Tran, (979) 458-5853 or vy@physics.tamu.edu; Dr. Casey Papovich, (979) 862-2704 or papovich@physics.tamu.edu; or Dr. Ryan Quadri, (979)862-2759 or quadri@physics.tamu.edu

Hutchins Shana

  • Dr. Casey Papovich

  • Dr. Ryan Quadri

  • Dr. Kim-Vy Tran

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