The James Webb Space Telescope’s spectacular image of the deep-infrared Universe has uncovered 42 new lensed images of galaxies and revealed at unprecedented depth the shape of the lens that could eventually help us see the very first galaxies.
The revelation of James Webb Space Telescope Deep field image of US President Joe Biden in a special Event at the White House on July 11 was a closely guarded secret. Teams of astronomers rushed to be the first to analyze it, with three new articles appearing on the community’s preprint server within a week of the image’s release.
“We kind of got brushed aside, to be honest!” Brenda Frye, an astronomer at the Steward Observatory at the University of Arizona and co-author of one of the papers, told Space.com. “Usually we have a year or two warning, but nobody saw it [this release] come about this time.”
That galaxy The cluster SMACS J0723.3-7327, called SMACS J0723 for short, is one of a series of galaxy clusters that Webb is imaging for various gravitational lensing surveys. That being said, Frye said SMACS J0723 was nothing out of the ordinary — until now.
“It was a nice choice [to be one of the first images] because it was a relatively unknown destination,” she said.
gravitational lenses is a phenomenon in which the gravity of a very massive object distorts space into a shape consistent with an optical lens, causing light from whatever is behind the lens to be distorted and magnified in brightness. Galaxy clusters are particularly efficient lenses because they pack a huge mass (about 100 trillion solar masses in the case of SMACS J0723) into a relatively compact volume about 3 to 5 million light-years across.
Previous polls Hubble Space Telescope and the retirees Herschel Space Observatory found a handful of lens images of background galaxies during their SMACS J0723 observations. But Webb takes the hunt to a whole new level.
Frye’s team, led by University of California, Berkeley graduate student Massimo Pascale, discovered 42 new lens images in the background of the new deep-field image. Gravitational lensing can create multiple images of the same galaxy, so these 42 images represent 19 individual galaxies. Another team led by Gabriel Caminha from the Max Planck Institute for Astrophysics in Germany counted 27 new lens images.
Whatever the end result, these lensed images allow scientists to create a map of matter — both visible and dark – is distributed in the cluster SMACS J0723 and in turn models the shape of the lens. One of the new works by a team led by Durham University’s Guillaume Mahler concluded that most of the mass is concentrated in the brightest and most massive galaxy in the cluster.
“Not only do our models describe mass, but we can use them to describe the magnification of these lens images,” Pascale told Space.com.
The currently most distant confirmed galaxy is a distant object known as GN-z11which 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 light wavelength that occurs as the universe expands between a distant object and the viewer. The higher the redshift factor, the further away the light source is.)
An even more distant candidate is HD1, discovered at redshift 13, appears to us as it was just 300 million years after the Big Bang. Even more recently early results of Webb have identified another candidate galaxy at redshift 13 called GLASS-z11. However, astronomers have not yet confirmed the redshifts of HD1 or GLASS-z11.
Webb is expected to break both of these redshift records, although it remains to be determined if any of the lensing galaxies seen in SMACS J0723 are more distant than Gn-z11 or HD1. Pascale and Frye are interested in imaging a phenomenon called the “critical curve” because it is along these curves that gravitational lensing applies the greatest magnifying power and astronomers have the best chance of seeing them very first galaxies.
“The typical magnification in a lens cluster is about a factor of 10, and that’s not enough to see the first galaxies,” Frye said. “But if we look near the critical curve, things get magnified a hundred or even a thousand times.”
Think of a critical curve as a contour line on a topographic map of the sea’s surface Earth. The more such contour lines are clustered together, the greater the elevation of a given point on the surface. Similarly, a critical curve is where the contour lines of gravitational potential converge, and the more concentrated they are, the greater that potential and attendant magnification. The location and shape of the lens images can give an indication of where the critical curve lies.
“Ultimately, we want to look closely along the critical curve, where magnification is highest, and that’s where we’ll find the highest redshift galaxies,” Frye said.
For this reason, the initial trio of new work on the Webb depth field focuses on modeling the amount and distribution of matter in the foreground cluster, and consequently the shape of the lens and the position of the critical curve.
However, the modeling can also tell us something about the galaxy cluster’s own history.
“We found that the mass distribution is a bit more elongated than expected,” Pascale said. “Maybe that says something about them Cluster merger historyand we can extrapolate from that and learn about clustering as a whole, which takes place in a very chaotic environment, where heaviness from all these galaxies pulls together.”
The immediate next step for Pascale and Frye’s team and the authors of the other two articles is to go through the peer review process to see these results published in scientific journals. Additionally, data from Webb’s NIRISS (Near Infrared Imager and Slitless Spectrograph) awaits analysis and should help scientists determine the spectroscopic redshifts of the lensing galaxies and see how far away they are. (The low-field image was captured by NIRCam, the near-infrared camera.)
“Before Webb pictured it, SMACS J0723 wasn’t the star of the show,” Pascale said. “Now all of a sudden there’s paper after paper, which really speaks to the power of Webb to reveal things we couldn’t see before.”