Dazzling James Webb Space Telescope Image Accelerates Science Fight

A breathtaking deep-infrared image of the universe by the James Webb Space Telescope has revealed 42 new images of lensed galaxies and revealed an unprecedented depth of lens shape that could eventually help us see the very first galaxies.

The release of the deep-field image of the James Webb Space Telescope by US President Joe Biden at a special event at the White House on July 11 was a closely guarded secret. Teams of astronomers sought to be the first to analyze it, and within a week of the image’s release, three new papers were submitted to the community preprint server.

“Honestly, we were a little taken aback!” was told this by Brenda Fry, an astronomer at the Steward Observatory at the University of Arizona and co-author of one of the papers. “Usually we have a warning for a year or two, but no one has seen [this release] will come at this time.”

Gallery: First photos of the James Webb Space Telescope
Related: How the James Webb Space Telescope works in pictures

The galaxy cluster SMACS J0723.3-7327, known as SMACS J0723 for short, is among the galaxy clusters that Webb visualizes for various gravitational lensing surveys. Beyond that, according to Fry, there was nothing exceptional about SMACS J0723—until now.

“Wonderfully chosen [to be one of the first images] because it was a relatively unknown target,” she said.

Gravitational lensing is a phenomenon in which the gravity of a very massive object warps space into a shape similar to an optical lens, causing the light from what is behind the lens to be distorted and increase in brightness. Galaxy clusters are particularly effective lenses because they pack a huge amount of mass (in the case of SMACS J0723, about 100 trillion times the mass of the Sun) into a relatively compact volume 3 to 5 million light-years in diameter. .

Previous surveys by the Hubble Space Telescope and the former Herschel Space Observatory found several lens images of background galaxies in their observations of SMACS J0723. But Webb takes hunting to a whole new level.

Fry’s team, led by UC Berkeley graduate student Massimo Pascal, discovered 42 new lensed images against a new deep-field image. Gravitational lenses can create multiple images of the same galaxy, so these 42 images represent 19 separate galaxies. Another team, led by Gabriel Caminha of the Max Planck Institute for Astrophysics in Germany, counted 27 new lens images.

Whatever the final result, these lens images allow scientists to fine-tune a map of how matter – both visible and dark – is distributed in the SMACS J0723 cluster and, in turn, model the shape of the lens. In one of the new papers, a group led by Guillaume Mahler of Durham University concluded that most of the mass is concentrated in the brightest and most massive galaxy in the cluster.

Examples of some lensed background galaxies in the Webb image SMACS J0723. (Image credit: NASA/ESA/CSA/STScI/Pascale et al.)

“Our models not only describe mass, but we can also use them to describe the magnification of these lens images,” Pascal told

So far, the most distant confirmed galaxy is a distant object known as GN-z11, which has a redshift of 11.09, meaning we see it as it existed 13.4 billion years ago, just 400 million years after Big bang. (“Redshift” refers to the stretching of the wavelength of light that occurs when the universe expands between a distant object and an observer. The higher the redshift factor, the further away the light source.)

An even more distant candidate, HD1, found at redshift 13, appears to us as it was just 300 million years after the Big Bang. More recently, early results by Webb have identified another redshift 13 candidate galaxy called GLASS-z11. However, astronomers have yet to confirm the redshift of either HD1 or GLASS-z11.

Webb is expected to break both of these redshift records, although it remains to be determined whether any of the lensed galaxies seen in SMACS J0723 are more distant than Gn-z11 or HD1. Pascal and Fry are interested in mapping a phenomenon called the “critical curve” because it is along these curves that the gravitational lens exerts the most magnifying force, and it is here that astronomers have the best chance of seeing the very first galaxies.

“Typical magnification in a lens cluster is about 10x, which is not enough to see the first galaxies,” Fry said. “But if we look at the critical curve, we see that here everything increases hundreds or even thousands of times.”

Think of the critical curve as contour lines on a topographic map of the Earth’s surface. The more such contour lines grouped together, the greater the height of any particular spot on the surface. Similarly, the critical curve is where the contour lines of the gravitational potential are clustered, and the more they cluster, the stronger this potential and the increase that accompanies it. The location and shape of lensed images can indicate where the critical curve lies.

Examples of some lensed background galaxies in the Webb image SMACS J0723. (Image credit: NASA/ESA/CSA/STScI/Pascale et al.)

“Ultimately, we want to look straight along the critical curve where the magnification is greatest, and that’s where we’ll find the galaxies with the highest redshift,” Fry said.

This is why the original three new papers on Webb’s deep field focus on modeling the amount and distribution of matter in a foreground cluster and hence on the shape of the lens and the location of the critical curve.

However, simulations can also tell us about the galaxy cluster’s own history.

“We found that the mass distribution was a bit more elongated than expected,” Pascal said. “Perhaps this says something about the history of the cluster merger, and we can extrapolate this and learn something about the formation of the cluster as a whole, which takes place in a very chaotic environment, where the gravity of all these galaxies attracts each other.”

The next immediate step for the team of Pascal and Fry, as well as the authors of the other two papers, will be to go through a peer review process to see the results published in scientific journals. In addition, data from Webb’s NIRISS (near infrared imaging instrument and slitless spectrograph) is awaiting analysis and should help scientists determine the spectroscopic redshifts of lensed galaxies and see how far away they are. (The deep field image was captured by the NIRCam near-infrared camera.)

“Before Webb photographed it, SMACS J0723 was not the star of the show,” Pascal said. “Now, all of a sudden, it’s got paper after paper on it that really speaks to how powerful Webb is to uncover things we couldn’t see before.”

The preprint paper by Pascal and Fry can be found here. Two other documents are available here and here.

Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and on Facebook.

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