Abell 2744, Pandora's Cluster, MACS J0416.1-2403, MACS J0717.5+3745, MACS J1149.5+2223. Credit: NASA, ESA, and J. Lotz and M. Mountain (STScI). Release Images
NASA's Great Observatories are teaming up to look deeper into the
universe than ever before. With a boost from natural "zoom lenses"
found in space, they should be able to uncover galaxies that are as
much as 100 times fainter than what the Hubble, Spitzer, and Chandra
space telescopes can typically see.
This ambitious collaborative program is called The Frontier Fields.
Astronomers will spend the next three years peering at six massive
clusters of galaxies. Researchers are interested not only as to what's
inside the clusters, but also what's behind them. The gravitational
fields of the clusters brighten and magnify distant background galaxies
that are so faint they would otherwise be unobservable.
The clusters themselves are among the most massive assemblages of matter known.
Astronomers anticipate that these observations will reveal
populations of never-before-seen galaxies that existed when the universe
was only a few hundred million years old. The Hubble and Spitzer data
will be combined to measure the galaxies' distances and masses more
accurately than either observatory could measure alone, demonstrating
the synergy of these Great Observatories for such studies. The Chandra
X-ray Observatory will also peer deep into the fields, imaging them at
X-ray wavelengths to help determine the masses and lensing power of the
clusters, as well as identify background galaxies with massive black
holes.
"The idea is to use nature's natural telescopes in combination with
the Great Observatories to look much deeper than before and find the
most distant and faint galaxies we can possibly see," said principal
investigator Jennifer Lotz of the Space Telescope Science Institute
(STScI) in Baltimore, Md.
"We want to understand when and how the first stars and galaxies
formed in the universe, and each Great Observatory gives us a different
piece of the puzzle. Hubble tells you which galaxies to look at and
how many stars are being born in those systems. Spitzer tells you how
old the galaxy is and how many stars have formed," said Peter Capak,
the Spitzer principal investigator of the Frontier Fields program.
The high-resolution Hubble data from the Frontier Fields program will
also be used to trace the distribution of dark matter within the
foreground clusters. Accounting for the bulk of the universe's mass,
dark matter is the underlying, invisible scaffolding attached to
galaxies. "The apparent positions of those lensed galaxies then tell you
what's happening with the cluster itself, where the dark matter is in
that cluster," Lotz said. "We'll use that information to make a better
model of the cluster to better understand its lensing power."
The Hubble and Spitzer observations will be much more challenging for
researchers than previous deep fields that have been studied by this
powerful pair of observatories with great success. "With a deep image,
you've got a direct image — what you see is what you get. But when we
use a gravitational lens, background galaxies appear distorted and
brighter," Lotz said. "In order to understand the true properties of a
background galaxy, you have to understand how it is distorted and how it
is magnified. This depends on the distribution of dark matter in the
gravitational lens — the foreground cluster."
What's more, the galaxies seen in previous ultra-deep fields are just
the most massive at those epochs. "They are the tip of the iceberg. If
you want to see the galaxies that will turn into ones like our Milky
Way, you have to go much fainter," Lotz said. Without using the big
natural telescopes in space, astronomers would have to wait for the
James Webb Space Telescope. In fact, the Frontier Fields offer a sneak
peek of what the Webb telescope will routinely see anywhere it points
in space, when it is launched in 2018.
The Hubble Frontier Fields initiative grew out of high-level
discussions at STScI concerning what important, forward-looking science
Hubble should be doing in upcoming years. Despite several deep field
surveys, astronomers realized that a lot was still to be learned about
the distant universe. And, such knowledge would help in planning the
observing strategy for the Webb telescope.
To get a better assessment of whether doing more deep field
observations was scientifically interesting or urgent, STScI chartered a
"Hubble Deep Field Initiative" working group, which included U.S. and
European astronomers who were expert users of the Great Observatories.
The astronomers also considered synergies with other observatories,
such as Spitzer, Chandra, and the new Atacama Large Millimeter Array.
STScI Director Matt Mountain allocated his director's discretionary time
to the program.
The first object to be looked at this month is called Pandora's
Cluster (Abell 2744), which has been previously observed by all three
Great Observatories but not to the depth of the new observations. The
giant galaxy cluster appears to be the result of a simultaneous pile-up
of at least four separate, smaller galaxy clusters that took place
over a span of 350 million years.
Join several members of the Frontier Fields collaboration during
the live Hubble Hangout event at 4:00pm (EDT) on Thursday, October 24
to discuss more on what's to come from these observations, how the
clusters were chosen, and what we hope to learn from them. Visit: https://plus.google.com/u/0/events/cpl8pr6rjvls7en3c9ltrgelc80 .
CONTACT
Ray VillardSpace Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
Jennifer Lotz
Space Telescope Science Institute, Baltimore, Md.
410-338-4467
lotz@stsci.edu
