Conference

NASA’s Frontier Fields program has reached a critical point. The observations by NASA’s Great Observatories (Hubble, Spitzer, and Chandra) are nearing completion, and the full data are nearly all online for astronomers (or anybody else for that matter) to study. To herald this part of the program, the Frontier Fields were highlighted at the January American Astronomical Society (AAS) meeting in Grapevine, Texas, where over 2,500 astronomers gathered to discuss the cosmos. A new exhibit was displayed to help tell the story of the Frontier Fields program to the science community. We share that story with you below.

Shown here is the NASA Frontier Fields exhibit at the 229th AAS meeting, in Grapevine, Texas. Credit: Z. Levay (STScI)

NASA’s Great Observatories Team Up to View the Distant Universe

Shown here is NASA’s Hubble Space Telescope, which can observe ultraviolet light, visible light, and near-infrared light. Credit: NASA

Shown here is NASA’s Spitzer Space Telescope, which can observe infrared light. Credit: NASA

Shown here is NASA’s Chandra X-ray Observatory, which can observe high-energy X-rays. Credit: NASA

The Frontier Fields is a program developed collaboratively by the astronomical community. Despite the fact that observations are coming to an end, the wealth of data being added to NASA archives will ensure new discoveries for years to come.

The NASA Frontier Fields observations are providing the data for astronomers to

expand our understanding of how galaxies change with time
discover and study very distant galaxies
refining our mathematical models of gravitational lensing by galaxy clusters
explore the dark matter around galaxy clusters
analyze the light from supernovae
study the diffuse light emitted from gas within galaxy clusters
study how galaxy clusters change with time

A Sneak Peek at the First Billion Years of the Universe: Galaxy cluster fields extend the reach of the Great Observatories by allowing astronomers to use a technique called gravitational lensing, which magnifies background galaxies that are otherwise presently unobservable.

The observing plan of the NASA Frontier Fields program, using the galaxy cluster Abell 2744 and its adjacent parallel field as an example. Director’s Discretionary (DD) hours were allocated for Hubble and Spitzer observations. DD time comes directly from an observatory’s director, who has a set number of hours to allocate every year.

Advancing the Deep Field Legacy

Chandra, Hubble, and Spitzer are building upon more than two decades of deep-field initiatives with 12 new deep fields (six galaxy cluster deep fields and six deep fields adjacent to the galaxy cluster fields).

By using Hubble, Spitzer, and Chandra to study these deep fields in different wavelengths of light, astronomers can learn a great deal about the physics of galaxy clusters, galaxy evolution, and other phenomena related to deep-field studies. Observations with Hubble provide detailed information on galaxy structure and can detect some of the faintest, most distant galaxies ever observed via gravitational lensing. Spitzer observations help astronomers characterize the galaxies in the image, providing details on star formation and mass, for example. High-energy Chandra X-ray images probe the histories of the giant galaxy clusters by locating regions of gas heated by the collisions of smaller galaxy sub-clusters.

An example of images taken by Hubble, Spitzer, and Chandra of the Frontier Fields galaxy cluster Abell 2744 are shown below. These images show how astronomers can use color to highlight the type of light observed by each of NASA’s Great Observatories.

Processed original black-and-white images of galaxy cluster Abell 2744. Credit: Chandra – NASA/CXC/SAO; Hubble – NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI); Spitzer – NASA/JPL-Caltech/P. Capak

Processed images of galaxy cluster Abell 2744, with color added (X-ray light – blue, visible light – green, infrared light – red). Credit: Chandra – NASA/CXC/SAO; Hubble – NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI); Spitzer – NASA/JPL-Caltech/P. Capak

Processed composite image of galaxy cluster Abell 2744. Credit: Chandra – NASA/CXC/SAO; Hubble – NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI); Spitzer – NASA/JPL-Caltech/P. Capak

Developing Mathematical Models of the Clusters

By discovering background galaxies that are obviously multiply lensed, and measuring their distances, astronomers can use Einstein’s theory of general relativity to map out the distribution of mass (normal matter plus dark matter) for the galaxy cluster.

Once this mass distribution is known, astronomers can go back and look at regions where they expect the largest magnification of distant galaxies, again due to Einstein’s theory of general relativity. From these calculations, astronomers can develop magnification maps that highlight the regions where Hubble is most likely able to observe the most distant galaxies. This technique has allowed astronomers to detect ever-more distant galaxies in these fields and has helped astronomers better refine their models of mass distributions.

Mathematical models of the mass distribution of a galaxy cluster provide magnification maps that pinpoint the locations of greatest magnification due to gravitational lensing. These are where astronomers search for the most distant and faintest galaxies. Shown here are Hubble imagery of galaxy cluster Abell 2744 (green); distribution of mass for the Abell 2744 galaxy cluster (blue); and locations of greatest lensing for background galaxies with a redshift of 9 (pink). There are different magnification maps for background galaxies at different distances. Credit: J. Richard (CRAL Lyon), CATS team, and D. Coe (STScI)

Using mathematical models, astronomers can remove the foreground light from galaxies within a galaxy cluster. By removing the large-scale foreground light, astronomers are able to identify small-scale structures of background, faint, lensed galaxies. Shown here is galaxy cluster Abell 2744 before foreground light subtraction (left) and after foreground light subtraction (right). Multiple distant, faint galaxies become visible using this technique. Those in the circles are background galaxies that are possibly very distant, i.e., those with possibly very high redshifts. Credit: Livermore, Finkelstein, & Lotz 2016

Initial Discoveries

In the first few years of the program, over 85 refereed publications and 4 conferences have been devoted to or based, in part, on the Frontier Fields, including a workshop at Yale in 2014 and a meeting in Hawaii in 2015. Three types of science results are highlighted below.

Shown here are observations of the Frontier Fields galaxy cluster MACS J0717, taken by Chandra, Hubble, and the Jansky Very Large Array. Diffuse blue colors (Chandra X-ray Observatory) are from the light emitted by gas with temperatures of millions of degrees. Red, green, and blue (Hubble Space Telescope) colors are from galaxies. Diffuse pink colors (Jansky Very Large Array) are from excited gas from shock waves and turbulence due to merging galaxy clusters (middle-top and lower-left), as well as a foreground radio galaxy (center left). Credit: NASA, ESA, CXC, NRAO/AUI/NSF, STScI, and R. van Weeren (Harvard-Smithsonian Center for Astrophysics)

Shown here are gravitationally lensed galaxies in galaxy cluster MACS J0717, as observed by Hubble (left) and Spitzer (right). Credit: Hubble – NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI); Spitzer – NASA/JPL-Caltech/P. Capak

Shown here is supernova Refsdal (four points of light in the spiral arm of a distant background galaxy) multiply lensed by the foreground galaxy cluster MACS J1149. Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Studying the Histories of Merging Galaxy Clusters

Frontier Fields observations by NASA’s Great Observatories, along with additional ground-based observations, are building our understanding of the physics of massive galaxy-cluster mergers.

Studying Distant Galaxies

By studying Hubble Space Telescope deep imaging at the locations where gravitational lensing magnifications are predicted to be high, astronomers are detecting galaxies that are up to 100 times fainter* than those observed in the famous Hubble Ultra Deep Field. Infrared observations by the Spitzer Space Telescope enable astronomers to better understand the masses, and other characteristics, of background lensed galaxies and those residing within a massive galaxy cluster.

*Author note: this has been updated from 10 times fainter than the Hubble Ultra Deep Field to 100 times fainter than the Hubble Ultra Deep Field due to recent published results you can find, here.

Serendipitous Discoveries

In 2014, a multiply lensed supernova was discovered, providing a key test of the models of gravitational lensing. As predicted by the models, a new lensed version of the supernova appeared in 2015. Learn more about the appearance of a new lensed version of Refsdal here.

Looking to the Future

Both the James Webb Space Telescope (JWST, scheduled to launch in late 2018) and the Wide Field Infrared Survey Telescope (WFIRST, scheduled to launch in the mid-2020s) will greatly expand our understanding of galaxies and the distant universe.

Shown here are simulated Spitzer (left) and JWST (right) images of distant galaxies in infrared colors. These were constructed from a computer simulation of the deep universe. Credit: G. Snyder & Z. Levay (STScI)

Shown here are Hubble’s observations of Abell 2744 and parallel field (inset boxes), located inside the footprint of the WFIRST Wide Field Instrument. Credit: FF – NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI); DSS – STScI/NASA; Z. Levay (STScI)

JWST will build upon the success of Spitzer’s observations of the infrared universe with enhanced clarity and sensitivity, probing deeper into the universe than ever before. Due to the expansion of the universe, light from the most distant galaxies are shifted to redder wavelengths, moving beyond the visible spectrum and into infrared light. One of JWST’s primary science goals is to observe these infant galaxies at the edge of the observable universe.

Imagine having a Hubble-class telescope that can observe in the infrared and see greater than an order of magnitude more of the sky with each observation. WFIRST’s expansive field-of-view – 100 times wider than Hubble’s – will allow for new ground-breaking surveys of the deep universe.

From August 3-14, thousands of astronomers from around the world gathered in Honolulu, Hawaii, to discuss the latest astronomical discoveries at the International Astronomical Union (IAU) General Assembly. The Frontier Fields had a highly visible role during this two-week meeting, including a fascinating three-day focus meeting where all things Frontier Fields were discussed, including recent science results and the future of the Frontier Fields. In this post, I will highlight just a few of the Frontier Fields highlights at the IAU General Assembly.

The Frontier Fields was highlighted with a 3-day focus meeting at the International Astronomical Union general assembly meeting in Honolulu, Hawaii.

The Frontier Fields was highlighted with a three-day focus meeting at the International Astronomical Union General Assembly meeting in Honolulu, Hawaii. The focus meeting was kicked off with a great introductory talk by Dr. Jennifer Lotz (Principal Investigator of the Hubble Frontier Fields program).

A Wealth of Science

The Frontier Fields focus meeting covered much of the latest and greatest science results coming from the Frontier Fields program. Some of the new results included deeper understandings of galaxies in the distant universe, more complete pictures of the massive galaxy clusters, and the searches for exploding massive stars, called supernovae. Some big points of discussion at the focus meeting included the methods by which astronomers obtained and studied the Frontier Fields data. These methods included the analysis of the images and spectra as well as the development of physics-based models of gravitational lensing around the Frontier Fields galaxy clusters. The modeling efforts continue to be incredibly important because they tie our physics-based understanding of how gravitational lensing works with the observations of gravitational lensing, and they allow astronomers to accurately search for and study extremely distant and lensed galaxies.

We will highlight some of the new results in future blog posts.

As for the Hubble Frontier Fields, it was nice to see the progress on the observing campaign. Hubble is two-thirds of the way through its Frontier Fields observing campaign, having completed observations of four out of the six massive galaxy clusters and their four associated parallel fields. The completed Hubble Frontier Fields images are shown below.

Shown on the left is the galaxy cluster Abell 2744. Shown on the right is the adjacent parallel field. This was the first completed pair of targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Shown on the left is the galaxy cluster MACS J0416. Shown on the right is the adjacent parallel field. These were the second completed targets of the Hubble Frontier Fields program.

Shown on the left is the galaxy cluster MACS J0416. Shown on the right is the adjacent parallel field. This was the second pair of completed targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Shown on the left is the galaxy cluster MACS J0717. Shown on the right is the adjacent parallel field. These were the third pair of completed targets of the Hubble Frontier Fields program. This marked the halfway point of the Hubble Frontier Fields observing campaign and were completed in the Spring of 2015, around the 25th anniversary of the Hubble Space Telescope.

Shown on the left is the galaxy cluster MACS J0717. Shown on the right is the adjacent parallel field. This was the third pair of completed targets in the Hubble Frontier Fields program. This marked the halfway point of the Hubble Frontier Fields observing campaign. The MACS J0717 observations were completed in the spring of 2015, around the 25th anniversary of the Hubble Space Telescope.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Shown on the left is the galaxy cluster MACS J1149. Shown on the right is the adjacent parallel field. These were the fourth pair of completed targets of the Hubble Frontier Fields program.

Shown on the left is the galaxy cluster MACS J1149. Shown on the right is the adjacent parallel field. This was the fourth pair of completed targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

A Truly Multi-Mission Effort

Perhaps the most exciting aspect of the Frontier Fields focus meeting at the IAU was hearing from the multitude of ground- and space-based missions investigating the Frontier Fields. These observatories cover a wide range of the electromagnetic spectrum, from high-energy X-rays to low-energy radio waves. Scientific results were mentioned during this focus meeting from data obtained by the Hubble Space Telescope, the Chandra X-ray Observatory, the Jansky Very Large Array, the Very Large Telescope, the Atacama Large Millimeter/submillimeter Array, the Keck Observatory, the James Clerk Maxwell Telescope, the Herschel Space Observatory, and others. There was also a discussion of how the future James Webb Space Telescope will help us understand the cosmic frontier probed by the Frontier Fields.

With so many telescopes staring at these 12 patches of the sky, a wealth of data is being accumulated and studied that will keep astronomers busy for years to come. We truly expect the science from the Frontier Fields to redefine our understanding of massive galaxy clusters and the distant universe.

Sharing the Story

The Frontier Fields were highlighted in many other venues at the IAU meeting, not just during the Frontier Fields focus meeting. The Frontier Fields were a part of a Hubble 25th anniversary image gallery exhibit in the main concourse area of the convention center. A presentation was given to the astronomy education and outreach community about how the Frontier Fields are being incorporated into education and outreach products by the Office of Public Outreach at the Space Telescope Science Institute. Frontier Fields materials were available at the official NASA exhibit during the IAU meeting.

Perhaps the most stunning display of the Frontier Fields occurred at NASA’s hyperwall. The hyperwall is a high-definition video wall that provides a large and clear view of astronomical images and visualizations. Dr. Rachael Livermore (University of Texas, Austin) gave a visually stunning tour through Hubble’s Frontier Fields, including visualizations that highlighted the effects of gravitational lensing. Dr. Christine Jones (Harvard-Smithsonian Center for Astrophysics) gave a truly spectacular multiwavelength, multi-mission view of the Frontier Fields that included data from the Hubble Space Telescope, the Chandra X-ray Observatory, and the Jansky Very Large Array.

NASA’s hyperwall is always a big draw at professional astronomy meetings, public outreach events, and informal education venues. I highly encourage you to attend a hyperwall talk if you happen to be in the neighborhood of an event that has the NASA hyperwall. You can follow NASA’s hyperwall on Twitter – @NASAHyperwall .

The Frontier Fields were featured, in high-definition, on NASA's Hyperwall. Top - Rachael Livermore presents the current status of Hubble's Frontier Fields. Bottom - Christine Jones-Forman presents a multiwavelength view of the Frontier Fields.

Images from the Frontier Fields were featured, in high definition, on NASA’s hyperwall. Top: Dr. Rachael Livermore presents the current status of Hubble’s Frontier Fields. Bottom: Dr. Christine Jones presents a multiwavelength view of the Frontier Fields.