The Hubble Space Telescope has captured some of the farthest reaches of the universe with its deep field images, cosmic core samples of galaxies captured in tiny, focused sections of the night sky.
When astronomers discuss these observations, the question arises, again and again – is this an accurate representation of what the universe looks like? Or are these glimpses unique? And what else can we learn about the high-redshift universe, the distant regions of the cosmos Hubble’s successor, the James Webb Space Telescope, will observe upon its launch in 2018?
The Frontier Fields project arose at the Space Telescope Science Institute (STScI) in response to those recurring questions. As the Multi Cycle Treasury program, responsible for such projects as mapping the stellar content of the Andromeda Galaxy and creating wider-field galaxy surveys to complement the Hubble Ultra Deep Field, drew to a close, astronomers began discussing ideas for Hubble’s next big project. Discussions began in early 2012 over lunch meetings. “We are often asked by the public whether what is seen in the (Hubble Ultra Deep Field) is typical of the rest of the universe,” said Dr. Ken Sembach, Hubble Space Telescope mission head. “And quite frankly, we don’t know without further deep observations of this type.”
A second thread ran through the meetings – how else could we increase the immediate scientific return of the Webb Telescope in its first few years of operation. “The idea of setting the stage with multiple deep fields seemed like a good idea,” Sembach said, noting that the observations would both identify interesting objects for future observations with Webb and spur new scientific theories that Webb could clarify and expand upon. “We could wait for JWST, but why not do some more edge-of-the-universe exploring now?”
Sembach and STScI Director Matt Mountain contacted the Spitzer Space Telescope and Chandra X-ray Observatory directors to let them know that Hubble would be planning a new deep field initiative, and to ask them to join in the spirit of NASA Great Observatory cooperation.
Spitzer joined the collaboration and offered to devote some of the telescope’s discretionary time – time on the telescope set aside for the director to use on worthy projects. Chandra worked with the X-ray community to determine how to support the new deep field effort. The Chandra Guaranteed Time Observers team believed that further observations were necessary, and committed some of its time to observations of these fields.
To ensure the broad scientific goals of the astronomical community were met, STScI chartered a Hubble Deep Field Initiative working group made up of primarily of external scientists in the summer of 2012. The group, chaired by Dr. James Bullock of the University of California — Irvine, spent several months examining the scientific investigations that would be made possible by investing a substantial amount of Director’s Discretionary observing time in this project.
The working group also considered synergies with other observatories, including Spitzer, Chandra, and the Atacama Large Millimeter/submillimeter Array (ALMA). STScI made it a point to have scientists familiar with these observatories participate in the working group.
The working group returned a report to the STScI Director in late 2012. That report had a far richer, more cohesive, and more ambitious science program than originally envisioned. The science includes investigations of the content of distant galaxy clusters, populations of very faint galaxies, and dark and luminous matter. “In retrospect, the creation of that working group and that group’s commitment to producing a compelling science vision for these observations moved this idea from the realm of idea to one of reality,” Sembach said. “There is no doubt the program will produce tremendous science return.”
Due to the compelling science program envisioned by the working group, Hubble was committed to conducting this program. The project was made even stronger by the participation of other observatories, such as Spitzer and the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton). STScI started using the term “Frontier Fields” in November 2012 as it began to communicate the recommendations of the working group to the rest of the astronomical community.
STScI created an implementation team to begin the process of determining what would be needed to implement the science program recommended by the Hubble Deep Field Initiative working group. The team, chaired by Jennifer Lotz – who was also a member of the working group — selected the fields to observe, prepared the observing specifications, created a data pipeline to produce science products shortly after the observations are obtained, and worked with members of the community to collect additional information, such as lensing maps, in support of the program.
As the Frontier Fields project moves forward, it will unleash a flood of new science that will be made immediately available to the scientific community in the form of both raw observations and science products. The next several years promises a wealth of new data and discoveries that will continue to help alter and define humanity’s repository of astronomical knowledge.