The spectacular image of the Deep Infrared Universe from the James Webb Space Telescope has discovered 42 new lens images of galaxies and revealed the shape of the lens to unprecedented depth, potentially helping us see the very first galaxies.
The revelation of the James Webb Space Telescope deep field image, by US President Joe Biden in a special White House event held on July 11, was a closely guarded secret. Teams of astronomers raced to be the first to analyze it, with three new papers posted to the community preprint server within a week of the image’s release.
“We got a little swept away, to be honest!” Brenda Frye, an astronomer at the University of Arizona Steward Observatory and co-author of one of the papers, told Space.com. “Normally we have a year or two notice, but no one has seen [this release] arrive at this time.”
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The galaxy the SMACS J0723.3-7327 cluster, known as SMACS J0723 for short, is one of a set of galaxy clusters that Webb is imaging for various gravitational lensing surveys. Beyond that, Frye said, there was nothing exceptional about SMACS J0723 – until now.
“It was beautifully chosen [to be one of the first images] because it was a relatively unknown target,” she said.
Gravitational lens is a phenomenon in which the gravity of a very massive object warps space into a shape analogous to an optical lens, causing light distortion from whatever is behind the lens and amplified brightness. Galaxy clusters are particularly effective lenses because they pack an enormous amount of mass (in the case of SMACS J0723, about 100 trillion times the mass of the Sun) into a relatively compact volume with a diameter of about 3 to 5 million light-years in diameter. .
The previous surveys of The Hubble Space Telescope and retirees Herschel Space Observatory had found a handful of lens images of background galaxies in their SMACS J0723 observations. But Webb takes hunting to a whole new level.
Frye’s team, led by graduate student Massimo Pascale of the University of California, Berkeley, discovered 42 new lens images in the background of the new deep-field image. Gravitational lenses can create multiple images of the same galaxy, so these 42 images represent 19 individual galaxies. Another team, led by Gabriel Caminha of the Max Planck Institute for Astrophysics in Germany, counted 27 new lens images.
Whatever the final tally, these lensed images allow scientists to refine a map of how matter – both visible and dark — is distributed in the SMACS J0723 cluster, and in turn models the shape of the lens. One of the new papers, from a team led by Guillaume Mahler of Durham University, concluded that most of the mass is centered in the brightest and most massive galaxy in the cluster.
“Our models not only describe the mass, but we can also use them to describe the magnification of these lensed images,” Pascale told Space.com.
The current most distant confirmed galaxy is a distant object known as the 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 the big Bang. (“Redshift” refers to the stretching of the wavelength of light that occurs as the universe expands between a distant object and the viewer. The higher the redshift factor, the stronger the light source is far away.)
An even more distant candidate is HD1, discovered at a redshift of 13, appears to us as it was barely 300 million years after the Big Bang. Even more recently, Webb’s first results have identified another candidate galaxy for redshift 13, called GLASS-z11. However, astronomers have yet to confirm the redshifts of 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 further away than Gn-z11 or HD1. Pascale and Frye are interested in mapping a phenomenon called a “critical curve”, because it is along these curves that gravitational lensing applies the greatest magnifying power, and where astronomers are most likely to To see the very first galaxies.
“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, that’s where things get magnified hundreds or even thousands of times.”
Think of a critical curve as being like contour lines on a topographic map of the surface of the Earth. The more these contour lines are grouped together, the greater the height of a particular point on the surface. Similarly, a critical curve is where the contour lines of gravitational potential cluster together, and the more clustered they are, the stronger that potential and the accompanying magnification. The location and shape of the lens images can give an indication of where the critical curve is.
“Ultimately what we want to do is look along the critical curve where the magnification is highest, and that’s where we’ll find the highest redshift galaxies,” Frye said.
This is why Webb’s initial trio of new deep-field papers focus on modeling the amount and distribution of matter in the foreground cluster, and hence the shape of the lens and the location of the critical curve.
However, the modeling can also tell us about the galaxy cluster’s own history.
“We found the mass distribution to be a little more stretched out than expected,” Pascale said. “Maybe that says a lot about the cluster merge historyand we can extrapolate from that and learn something about cluster formation as a whole, which happens in a very chaotic environment where gravity of all these galaxies attract each other.”
The immediate next step for Pascale and Frye’s team, and the authors of the other two papers, is to go through the peer review process to see these results published in scientific journals. Beyond that, data from Webb’s NIRISS (Near Infrared Imager and Slitless Spectrograph) is awaiting analysis and should help scientists determine the spectroscopic redshifts of lensed galaxies and see how far apart they are. are found. (The deep-field image was captured by NIRCam, the near-infrared camera.)
“Before Webb imagined it, SMACS J0723 wasn’t the star of the show,” Pascale said. “Now suddenly there’s paper after paper on it, which really shows how powerful Webb is, in revealing things that we couldn’t see before.”
The prepublication of Pascale and Frye’s article can be found here. The other two items are available here and here.
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