In the ongoing hunt for the universe's earliest galaxies, NASA's
Spitzer Space Telescope has wrapped up its observations for the Frontier
Fields project. This ambitious project has combined the power of all
three of NASA's Great Observatories -- Spitzer, the Hubble Space
Telescope and the Chandra X-ray Observatory -- to delve as far back in
time and space as current technology can allow.
Even with today's best telescopes, it is difficult to gather enough
light from the very first galaxies, located more than 13 billion light
years away, to learn much about them beyond their approximate distance.
But scientists have a tool of cosmic proportions to help in their
studies. The gravity exerted by massive, foreground clusters of galaxies
bends and magnifies the light of faraway, background objects, in effect
creating cosmic zoom lenses. This phenomenon is called gravitational
lensing.
The Frontier Fields observations have peered through the strongest
zoom lenses available by targeting six of the most massive galaxy
clusters known. These lenses can magnify tiny background galaxies by as
much as a factor of one hundred. With Spitzer's new Frontier Fields
data, along with data from Chandra and Hubble, astronomers will learn
unprecedented details about the earliest galaxies.
"Spitzer has finished its Frontier Fields observations and we are
very excited to get all of this data out to the astronomical community,"
said Peter Capak, a research scientist with the NASA/JPL Spitzer
Science Center at Caltech in Pasadena, California, and the Spitzer lead
for the Frontier Fields project.
A recent paper published in the journal Astronomy & Astrophysics
presented the full catalog data for two of the six galaxy clusters
studied by the Frontier Fields: Abell 2744 -- nicknamed Pandora's
Cluster -- and MACS J0416, both located about four billion light years
away. The other galaxy clusters selected for Frontier Fields are RXC
J2248, MACS J1149, MACS J0717 and Abell 370.
Eager astronomers will comb the Frontier Fields catalogs for the
tiniest, dimmest-lensed objects, many of which should prove to be the
most distant galaxies ever glimpsed. The current record-holder, a galaxy
called GN-z11, was reported in March
by Hubble researchers at the astonishing distance of 13.4 billion
light-years, only a few hundred million years after the big bang. The
discovery of this galaxy did not require gravitational lenses because it
is an outlying, extremely bright object for its epoch. With the
magnification boost provided by gravitational lenses, the Frontier
Fields project will allow researchers to study typical objects at such
incredible distances, painting a more accurate and complete picture of
the universe's earliest galaxies.
Astronomers want to understand how these primeval galaxies arose, how
their constituent mass developed into stars, and how these stars have
enriched the galaxies with chemical elements fused in their
thermonuclear furnaces. To learn about the origin and evolution of the
earliest galaxies, which are quite faint, astronomers need to collect as
much light as possible across a range of frequencies.
With sufficient light from these galaxies, astronomers can perform spectroscopy, pulling out details about stars' compositions, temperatures and their environments by examining the signatures of chemical elements imprinted in the light.
With sufficient light from these galaxies, astronomers can perform spectroscopy, pulling out details about stars' compositions, temperatures and their environments by examining the signatures of chemical elements imprinted in the light.
"With the Frontier Fields approach," said Capak, "the most remote and
faintest galaxies are made bright enough for us to start to say some
definite things about them, such as their star formation histories."
Because the universe has expanded over its 13.8-billion-year history,
light from extremely distant objects has been stretched out, or
redshifted, on its long journey to Earth. Optical light emitted by stars
in the gravitational-lensed, background galaxies viewed in the Frontier
Fields has therefore redshifted into infrared. Spitzer can use this
infrared light to gauge the population sizes of stars in a galaxy, which
in turn gives clues to the galaxy's mass. Combining the light seen by
Spitzer and Hubble allows astronomers to identify galaxies at the edge
of the observable universe.
Hubble, meanwhile, scans the Frontier Fields galaxy clusters in
optical and near-infrared light, which has redshifted from ultraviolet
light on its journey to Earth. Chandra, for its part, observes the
foreground galaxy clusters in high-energy X-rays emitted by black holes
and ambient hot gas. Along with Spitzer, the space telescopes size up
the masses of the galaxy clusters, including their unseen but
substantial dark matter content. Nailing down the clusters' total mass
is a critical step in quantifying the magnification and distortion they
produce on background galaxies of interest. Recent multi-wavelength
results in this vein from the Frontier Fields project regarding the MACS
J0416 and MACS J0717 clusters were published in October 2015 and
February 2016. These results also brought in radio wave observations
from the Karl G. Jansky Very Large Array to see star-forming regions
otherwise hidden by gas and dust.
The Frontier Fields collaboration has inspired scientists involved in
the effort as they look ahead to delving even deeper into the universe
with the James Webb Space Telescope, which is planned for launch in
2018.
"The Frontier Fields has been an entirely community-led project,
which is different from the way many projects of this magnitude are
typically pursued," said Lisa Storrie-Lombardi of the Spitzer Science
Center, also with the Frontier Fields project. "People have gotten
together and really embraced Frontier Fields."
In addition to the six Frontier Fields galaxy clusters, Spitzer has
done follow-up observations on other, slightly shallower fields Hubble
has gazed into, expanding the overall number of cosmic regions where
fairly deep observations have been taken. These additional fields will
further serve as rich areas of investigation for Webb and future
instruments.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the
Spitzer Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at Caltech. Spacecraft operations are based at Lockheed Martin
Space Systems Company, Littleton, Colorado. Data are archived at the
Infrared Science Archive, housed at the Infrared Processing and Analysis
Center at Caltech. Caltech manages JPL for NASA.
For more information about Spitzer, visit: http://www.nasa.gov/spitzer - http://spitzer.caltech.edu
Written by Adam Hadhaz
News Media Contact
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov
Source: JPL-Caltech
