Webb’s infrared image of the galaxy
cluster El Gordo (“the Fat One”) reveals hundreds of galaxies, some never
before seen at this level of detail. El Gordo acts as a gravitational lens,
distorting and magnifying the light from distant background galaxies. Image:
NASA, ESA, CSA. Science: Jose Diego (Instituto de Física de Cantabria), Brenda
Frye (University of Arizona), Patrick Kamieneski (Arizona State University),
Tim Carleton (Arizona State University), and Rogier Windhorst (Arizona State
University). Image processing: Alyssa Pagan (STScI), Jake Summers (Arizona
State University), Jordan D’Silva (University of Western Australia), Anton
Koekemoer (STScI), Aaron Robotham (University of Western Australia), and Rogier
Windhorst (Arizona State University).
Download the full-resolution
version from the Space Telescope Science Institute.
A new image of the galaxy cluster
known as “El Gordo” is revealing distant and dusty objects never seen before,
and providing a bounty of fresh science. The infrared image, taken by NASA’s
James Webb Space Telescope, displays a variety of unusual, distorted background
galaxies that were only hinted at in previous Hubble Space Telescope
images.
El Gordo is a cluster of hundreds
of galaxies that existed when the universe was 6.2 billion years old, making it
a “cosmic teenager.” It’s the most massive cluster known to exist at that time.
(“El Gordo” is Spanish for the “Fat One.”)
The team targeted El Gordo because
it acts as a natural, cosmic magnifying glass through a phenomenon known
as gravitational lensing. Its powerful gravity bends and
distorts the light of objects lying behind it, much like an eyeglass lens.
“Lensing by El Gordo boosts the
brightness and magnifies the sizes of distant galaxies. This lensing effect
provides a unique window into the distant universe,” said Brenda Frye of the
University of Arizona. Frye is co-lead of the PEARLS-Clusters branch of the
Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) team
and lead author of one of four papers analyzing the El Gordo
observations.
The Fishhook
Within the image of El Gordo, one
of the most striking features is a bright arc represented in red at upper
right. Nicknamed “El Anzuelo” (The Fishhook) by one of Frye’s students, the
light from this galaxy took 10.6 billion years to reach Earth. Its distinctive
red color is due to a combination of reddening from dust within the galaxy
itself and cosmological redshift due to its extreme distance.
By correcting for the distortions
created by lensing, the team was able to determine that the background galaxy
is disk-shaped but only 26,000 light-years in diameter – about one-fourth the
size of the Milky Way. They also were able to study the galaxy’s star formation
history, finding that star formation was already rapidly declining in the
galaxy’s center, a process known as quenching.
“We were able to carefully dissect
the shroud of dust that envelops the galaxy center where stars are actively
forming," said Patrick Kamieneski of Arizona State University, lead author
on a second paper. "Now, with Webb, we can peer through this thick
curtain of dust with ease, allowing us to see firsthand the assembly of
galaxies from the inside out."
Two of the most prominent features
in the image include the Thin One, highlighted in box A, and the Fishhook, a
red swoosh highlighted in box B. Both are lensed background galaxies. The
insets at right show zoomed-in views of both objects. Image: NASA, ESA, CSA.
Science: Jose Diego (Instituto de Física de Cantabria), Brenda Frye (University
of Arizona), Patrick Kamieneski (Arizona State University), Tim Carleton
(Arizona State University), and Rogier Windhorst (Arizona State University).
Image processing: Alyssa Pagan (STScI), Jake Summers (Arizona State
University), Jordan D’Silva (University of Western Australia), Anton Koekemoer
(STScI), Aaron Robotham (University of Western Australia), and Rogier Windhorst
(Arizona State University).
Download the
full-resolution version from the Space Telescope Science Institute.
The Thin One
Another prominent feature in the
Webb image is a long, pencil-thin line at left of center. Known as “La Flaca”
(the Thin One), it is another lensed background galaxy whose light also took
nearly 11 billion years to reach Earth.
Not far from La Flaca is another
lensed galaxy. When the researchers examined that galaxy closely, they found a
single red giant star that they nicknamed Quyllur, which is the Quechua term
for star.
Previously, Hubble has found other
lensed stars (such as Earendel), but they were all blue
supergiants. Quyllur is the first individual red giant star observed beyond 1
billion light-years from Earth. Such stars at high redshift are only detectable
using the infrared filters and sensitivity of Webb.
“It's almost impossible to see
lensed red giant stars unless you go into the infrared. This is the first one
we’ve found with Webb, but we expect there will be many more to come,” said
Jose Diego of the Instituto de Física de Cantabria in Spain, lead author of
a third paper on El Gordo.
Galaxy Group and Smudges
Other objects within the Webb
image, while less prominent, are equally interesting scientifically. For
example, Frye and her team (which includes nine students from high school to
graduate students) identified five multiply lensed galaxies which appear to be
a baby galaxy cluster forming about 12.1 billion years ago. There are another
dozen candidate galaxies which may also be part of this distant cluster.
“While additional data are required
to confirm that there are 17 members of this cluster, we may be witnessing a
new galaxy cluster forming right before our eyes, just over a billion years
after the big bang,” said Frye.
A final paper examines very faint,
smudge-like galaxies known as ultra-diffuse galaxies. As their name suggests,
these objects, which are scattered throughout the El Gordo cluster, have their
stars widely spread out across space. The team identified some of the most
distant ultra-diffuse galaxies ever observed, whose light traveled 7.2 billion
years to reach us.
“We examined whether the properties
of these galaxies are any different than the ultra-diffuse galaxies we see in
the local universe, and we do actually see some differences. In particular,
they are bluer, younger, more extended, and more evenly distributed throughout
the cluster. This suggests that living in the cluster environment for the past
6 billion years has had a significant effect on these galaxies,” explained
Timothy Carleton of Arizona State University, lead author on the fourth paper.
“Gravitational lensing was
predicted by Albert Einstein more than 100 years ago. In the El Gordo cluster,
we see the power of gravitational lensing in action,” concluded Rogier
Windhorst of Arizona State University, principal investigator of the PEARLS
program. “The PEARLS images of El Gordo are out-of-this-world beautiful. And,
they have shown us how Webb can unlock Einstein's treasure chest.”
The paper by Frye et al. has been published in the
Astrophysical Journal. The paper by Kamieneski et al. has been accepted for publication
in the Astrophysical Journal. The paper by Diego et al. has been published in Astronomy
& Astrophysics. The paper by Carleton et al. has been accepted for
publication in the Astrophysical Journal.
The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Source: Webb
Spotlights Gravitational Arcs in ‘El Gordo’ Galaxy Cluster | NASA
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