Distant galaxies in Webb images suggest we need to rethink star and galaxy evolution in the early universe.

Webb's first deep field
Webb's first image, revealed on Monday, July 11th, shows thousands of galaxies in a tiny sliver of sky. Many galaxies are part of a massive cluster named SMACS 0723, but the image reveals far more distant ones, too. The heft of the galaxies and the dark matter around them lenses background galaxies, distorting their shapes but also magnifying them and making them easier to see.

The very first results from the James Webb Space Telescope seem to indicate that massive, luminous galaxies had already formed within the first 250 million years after the Big Bang. If confirmed, this would seriously challenge current cosmological thinking. For now, however, that’s still a big “if.”

Shortly after NASA published Webb’s first batch of scientific data, the astronomical preprint server arXiv was flooded with papers claiming the detection of galaxies that are so remote that their light took some 13.5 billion years to reach us. Many of these appear to be more massive than the standard cosmological model that describes the universe’s composition and evolution.

“It worries me slightly that we find these monsters in the first few images,” says cosmologist Richard Ellis (University College London).

Hunting for Distant Galaxies

JWST deep-field image showing many galaxies
This image is part of a larger mosaic taken with the Near Infrared Camera (NIRCam) on the James Webb Space Telescope. It’s from a patch of sky near the handle of the Big Dipper. This is one of the first images obtained by the Cosmic Evolution Early Release Science Survey (CEERS) collaboration. Distant galaxies will show up in many JWST images, but CEERS is one of the surveys specifically set up to help find them.
NASA / STScI / CEERS / TACC / S. Finkelstein / M. Bagley / Z. Levay

Young, massive stars in newborn galaxies emit vast amounts of energetic ultraviolet radiation. As this light moves through expanding space for billions of years, the wavelengths stretch (redshift) all the way into the infrared – radiation that Webb’s instruments are sensitive to.

It takes careful spectroscopic measurements – either by Webb’s spectrometers or by the ground-based ALMA observatory that operates at even longer wavelengths – to precisely determine the redshifts, which tells you how far out into space — and thus how far back in time — you’re looking. But there’s a quick (albeit less reliable) workaround that gives a rough idea.

Neutral hydrogen atoms in intergalactic space absorb ultraviolet radiation at wavelengths shorter than 91.2 nanometers. For remote objects, this threshold also redshifts to longer wavelengths, into the infrared for the most distant galaxies. Since Webb’s near-infrared camera NIRCam takes measurements through a large number of filters, each covering a different wavelength band, a galaxy may be visible in some channels but not in others. The wavelength band in which the galaxy disappears roughly indicates its redshift, and the corresponding look-back time.

Distant galaxy seen in different wavelength filters
These postage-stamp images taken by JWST's near-infrared camera show the galaxy CEERS-93316 in six different filters: F115W, F150W, F200W, F277W, F356W, and F444W.
Donnan et al. 2022

Just six days after Webb’s first science data became available, on July 19th, two independent teams of astronomers presented their analysis based on this technique. Both groups, one led by Rohan Naidu (Center for Astrophysics, Harvard & Smithsonian) and the other by Marco Castellano (Rome Observatory, Italy), found two relatively bright galaxy candidates at redshifts of about 11 and 13, residing in a universe on the order of 400 and 325 million years old, respectively.

In the days that followed, another two independent teams, led by Callum Donnan (University of Edinburgh) and by Yuichi Harikane (University of Tokyo), announced the tantalizing find of an unexpectedly massive galaxy at a redshift of 17. That corresponds to looking back to just 225 million years after the Big Bang.

In yet another study, Haojing Yan (University of Missouri) and his colleagues even claimed that some of their candidate galaxies might reach a redshift of 20 (180 million years after the Big Bang).

“It’s understandable that young teams are racing ahead” to put out their results, says Ellis. According to extragalactic astronomer Mariska Kriek (Leiden Observatory), some of these groups may have written large parts of their paper in advance, so they only had to fill in a couple of numbers and other details. “They have picked the low-hanging fruit,” she says. “For some people, it’s just very important to be first. And of course everyone is very curious about what’s in the data.”

Before the community accepts these claims, the reported redshifts have to be confirmed spectroscopically. Mark McCaughrean, the senior science adviser of the European Space Agency (a major partner on Webb) commented on Twitter: “I’m sure some of them will be [confirmed], but I’m equally sure they won’t all be. […] It does all feel a little like a sugar rush at the moment.”

Ellis agrees: “It’s one thing to put a paper on arXiv,” he says, “but it’s quite something else to turn it into a lasting article in a peer-reviewed journal.”

So far, astronomers have found distant galaxy candidates in four areas of the sky. Some scoured the neighborhood of SMACS 0723-73, the galaxy cluster in the southern constellation Volans (the Flying Fish) showcased in the first Webb image to be released. Others pored over two ongoing surveys, the Grism Lens-Amplified Survey from Space (GLASS) and the Cosmic Evolution Early Release Science (CEERS), in Sculptor and Boötes, respectively. In addition, three candidates were uncovered in another early-release image, the one of Stephan’s Quintet, a compact group of galaxies in Pegasus.

It’s hard to keep track of all the new findings, partly because each team uses its own numbering scheme. For instance, the galaxy candidate at a redshift of 17 is variously known as ID93316, CEERS-1749, and CR2-z17-1.

This galaxy is also emblematic of some of the problems with detecting distant galaxies in this way. In fact, it has earned the nickname "Schrödinger’s Galaxy" because of its undecided nature — it turns out, it might actually be a much closer galaxy that's so dusty that it appears to disappear at longer wavelengths in the same way that more distant galaxies do. A team led by Jorge Zavala (National Astronomical Observatory of Japan), make the case that this galaxy is at a redshift of 5, corresponding to a lookback time of a “mere” 12.6 billion years.

“But it’s fun,” says Kriek. The fast pace of Webb science is keeping everyone on their toes, and there's a lot of work to do to confirm the most distant galaxies are really so far away. “Every day is a little adventure,” adds Ellis.

What Early Galaxies Say About the Universe

In many of the papers that have been posted so far, the authors state that their results, if confirmed, may challenge the standard model of cosmology. According to this model, known as Lambda Cold Dark Matter (ΛCDM), the universe’s evolution is governed by dark energy (denoted by the Greek letter lambda, Λ) and the equally mysterious cold dark matter (CDM), which makes up almost 85% of all matter.

According to ΛCDM, the very first galaxies could well show up at just 200 million years after the Big Bang, but they’d be puny and faint, resembling small dwarf galaxies. Instead, some of the remote candidate galaxies in the Webb data appear to contain about 1% of the mass of our Milky Way galaxy, which is already quite a lot at that early epoch.

Ivo Labbé (Swinburne University of Technology, Australia) and his colleagues even found one candidate at a redshift of 10 (500 million years after the Big Bang) that is already comparable in mass to our home galaxy. According to a recent study by Michael Boylan-Kolchin (University of Texas, Austin), ΛCDM predicts at most one such massive galaxy in a survey area that is 1,000 times larger.

But theorist David Spergel (Princeton University) is not yet alarmed. “I think that we need to be cautious about these statements,” he says. As Spergel explains, estimates for the mass of a remote galaxy are based on its observed luminosity at various wavelengths (which, incidentally, might be affected by ongoing instrument calibration). But the estimates also assume that the relative numbers of low-mass and high-mass stars are the same as in the Milky Way. However, higher pressures and temperatures in the early universe might have suppressed the formation of low-mass stars back then.

“At low redshifts, most of the mass is in low-mass stars,” Spergel says. “This may not be true at high redshifts. I suspect that we are learning that high-mass star formation was very efficient” in the early universe. Again, the final verdict has to await detailed spectroscopic follow-up observations. According to Kriek, astronomers will be vying for observing time on Webb to sort things out.

One thing’s for sure, though: in its first weeks of operation, the new space telescope has already surpassed most astronomers’ expectations. “It feels like opening a box of toys for the first time,” says Ellis. “It’s just fabulous.”

Editorial note: This article was updated with information from the Zavala et al. study, posted on the arXiv on August 3rd.



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August 10, 2022 at 8:51 pm

Very interesting report and JWST finding large redshift galaxies that may challenge LCDM model in BB. Using cosmology calculators, a galaxy with z = 17, light time or look back time distance = 13.494 Gyr, age at redshift = 0.228 Gyr after BB, comoving radial distance = 39.941 Gly so 4D space is expanding faster than c velocity to accept large redshift distance estimates in the BB model. https://lambda.gsfc.nasa.gov/toolbox/calculators.html

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August 11, 2022 at 1:54 pm

> The wavelength band in which the galaxy disappears roughly indicates
> its redshift, and the corresponding look-back time.

Having read (some of) the posted papers, this isn't all they're doing. With seven photometric bands (filters), which when de-redshifted basically correspond to the UV/optical part of the spectrum, they can compare the brightnesses in this crude broad "spectrum" with theoretical models based on local star-forming galaxies in the present era, thus deriving a "photometric redshift".

There is some possible confusion in this technique with active galactic nuclei (AGN) spectra (like Seyfert galaxies), which resemble the same kinds of emission spectra as star-forming regions, since both have hot, ionized gas.

Hopefully they can get IR spectra of these faint objects and measure the redshift from actual spectal lines.

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Monica Young

August 12, 2022 at 10:13 am

Exactly, the wavelength band in which a galaxy "disappears" indicates its photometric redshift. And you're absolutely right, there's a lot of work that remains to be done to confirm these candidates!

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Thomas Baytarian

August 12, 2022 at 5:20 pm

I've been right all my life!!!! And I knew the JWST was going to vindicate me. It JUST HAPPENED!
From early on I wanted to be an astronomer. It never happened. My parents wanted a doctor. And that was the only direction the money flowed. Yes that interested me, but it was not my passion. Thankfully before my mother and father died, I became a paramedic, and I think that made them happy in part. It was good to me, maybe better than being an astronomer, that's hard to say.
But I digress. I had a couple of points of interest, the formation of galaxies, and the age of the universe. I remember hatching brine shrimp and swirling the unhatched eggs in the round turtle tank I had. They formed a perfect galaxy shape. There was something about the formation of galaxies that we were missing, In fact we still haven't figured it out. But a few years back we discovered that all spiral galaxies have a supermassive black hole at it's center. This plays a major part in my other theory that the universe is WAY more than 14B years old.
I thought, well I believe they have a pretty good handle on the age of the earth. 4.5B years old. The earth of course is right here and we can see it, hold it and date it. But If the earth was 4.5 billion years old, how could it's existence be an entire 1/3 the age of the ENTIRE universe? Even if the current big bang theory was correct, this had a flaw.
The whole thing made absolutely no sense at all. Sure a lot of things don't fit into the common sense mold. But I felt that this certainly did (Not to brag, but I was tested In school and they found my common sense was at a nearly genius level.) After they found the central black holes, it intensified my belief and did nothing but fall into line with my theory.
I also believe that galaxies are huge matter recyclers. Streams of matter fall into the black hole and are broken down to basic particles, as they grow in size and are ejected at the poles, Only to reform stars and planets. The earth is made of the recycled material of black holes. There have been millions of earths that came before us. Therefore the universe is WAY more than 14B years old! The Hubble enforced my belief. The deep field images showed perfectly formed galaxies around 13B+ years ago. These galaxies must have formed well before the earth, and just after the "Big Bang". A hint of "maybe our theories are wrong" flowed thru the community.
Enter the Jason Web Space Telescope. Here is thing that will prove my theory! It took way longer than expected, I thought, please let me live long enough to see it's fruition, I will leave this world happy. Now I know I was right all along. Sure, there may have very well been a big bang, by it's very definition defies the laws of common sense. But it certainly didn't happen 15B years ago! The universe could very well be as I predict, infinite, and possibly infinitely old. Big Ban theorists meet the flat earthers. You have a lot in common.

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Deryk Houston

August 22, 2022 at 10:46 pm

I agree with Thomas. He may be completely wrong but one thing that has struck me all my life is the arrogance shown by astronomers. The don;t seem in the least bit shame faced when they add rediculous, unproven, unobserved crutches to keep the Big Bang alive and kicking.
At the very least....It has to be older.
Most likely though is that it is completely wrong.
I have tremendous respect for Physicists. I can't follow the math but I believe that they are on the right track.
Most astronomers on the other hand come across as more like the flat earthers.... they seem hell bent on proving that they are right even when the telescopes are telling them something different. (The Big Bang looks like someone from world war one covered in band aides, bandages and crutches.)

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August 13, 2022 at 1:38 pm

BB from the start is full of loop holes and created more questions than answers. The pointed origin of universe in hot densed tiny matter the so called "singularity " is unexplainable. More questions need to be answer such as "How the singularity started?, Whats the origin of singularity?, What was there before singularity exist?, What trigger the big bang? What was the characteristics of singularity and how it is so dense in a tiny matter?, How tiny was singularity? How long the singularity exist before the bb?' and many more. Im not astronomer but only an enthusiast of astronomy and im exited to witness JWST incoming more discoveries that will disproved this long standing "fantasy theory'

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August 13, 2022 at 11:08 pm

"Many of these appear to be more massive than the standard cosmological model that describes the universe’s composition and evolution."

This sentence doesn't read quite right. It seems some words may be left out; for instance, the writer may have intended to insert the words "predicted by" between "than" and "the."

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