In the JWST version of the Hubble Deep Field, astronomers are discovering what galactic life was like in the earliest years of the universe.

Galaxies spot a black field

NASA / ESA / CSA / Brant Robertson (UC Santa Cruz) / Ben Johnson (CfA) / Sandro Tacchella (Cambridge) / Marcia Rieke (University of Arizona) / Daniel Eisenstein (CfA); Image processing Alyssa Pagan (STScI)

The James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES) is basically the next-gen version of the Hubble Deep Field. But this newest, deep-sky stare is on a whole different level, with 32 days’ worth of telescope time, infrared wavelengths that allow JWST to see more distant galaxies than any telescope before it, and a much bigger viewing area than Hubble was capable of.

Even as the JADES program continues to collect data, team members Kevin Hainline (Steward Observatory) and Ryan Endsley (The University of Texas at Austin) announced at a press conference of the 242nd meeting of the American Astronomical Society the discovery of hundreds of early galaxies. These galaxies reveal the chaotic state of the universe as it was just hundreds of million years after the Big Bang.

Really Early Galaxies

The JADES team has so far discovered 717 galaxies at redshifts greater than 8, when the universe was just 600 million years old. The most distant of these — “the farthest galaxy humans have ever seen,” Hainline says — is spectroscopically confirmed to be at a redshift of 13.2, or just 325 million years after the Big Bang. If the entire history of the universe were a two-hour movie, then these galaxies are enabling us to watch, for the first time, scenes from the first two to five minutes.

Red blob in the middle of  black field, with a foreground white-orange galaxy to upper left
Color composite JWST NIRCam image of the galaxy JADES-GS-z13-0, the most distant, spectroscopically confirmed galaxy known so far.
NASA, ESA, CSA, and STScI, M. Zamani (ESA/Webb), L. Hustak (STScI). Science: B. Robertson (UCSC), S. Tacchella (Cambridge), E. Curtis-Lake (Hertfordshire), S. Carniani (Scuola Normale Superiore), and the JADES Collaboration

“This is important because we live in a universe of complexity, and the early universe was hydrogen, helium and light,” Hainline says. “These are the galaxies that are starting the process of making the elements and the complexity that we see in the world around us today.”

Before JWST, Hubble saw two luminous galaxies at such early times (redshifts greater than 10). Now, 93% of the galaxies JWST is picking up are new, never identified before. “This,” Hainline declares, “is the rest of the iceberg.”

The sample also provided opportunity for reassurance. Some in the community had been concerned that not all of these so-called early galaxies were really in the early universe. Astronomers first gauged their distances by a method that depended on measuring their brightness at each of several color bands. Using that method, it’s possible for dusty, relatively nearby galaxies to masquerade as more distant sources. But the JADES team assuaged that concern: Of 42 galaxies followed up with spectra, from which astronomers can obtain more fool-proof redshift measurements, there were no masqueraders.

What Was It Like Then?

The hundreds of galaxies offer a view almost into the very opening scenes of the cosmos, and they show that things were different then.

About a sixth of early galaxies in the JADES sample are in the throes of star formation of a kind we don’t see in the nearby universe, Endsley explains, marked by extremely bright emission at certain wavelengths. “Stars within very early galaxies are forming in these super-compact clumps,” he adds, “forming hundreds, perhaps thousands of these very massive, young stars all at once, basically within the span of a couple millions of years.”

But they weren’t “on” all the time. The low fraction of galaxies with such emission suggests that individual clumps would suddenly light up with new stars and then rest for some time. This “bursty” mode of star formation could explain the unexpectedly bright galaxies announced by other astronomers — they were simply looking at the galaxies fired up with unexpectedly intense star formation.

However, while these findings explain too-bright galaxies, they don’t explain the too-massive galaxies, another early, albeit controversial find from JWST data. Endsley explains that even as hot, massive newborn stars light up their galaxy, they’re not necessarily associated with all that much mass. “We're not really finding evidence of these over-massive objects within our JADES sample,” he states.

There’s a lot more to be gleaned from the JADES sample as JWST continues its observations, such as a better understanding of the galaxies’ shapes and sizes.

In addition, while stars (and associated dust) dominated the press conference, these galaxies’ central black holes are waiting their turn for center stage. “I think that there are some really exciting examples of active supermassive black holes that people didn't necessarily expect to exist in this very early episode of the universe,” Endsley says. “It is something we really need to start taking into consideration as we move forward.”

In the meantime, JWST has already painted a chaotic picture of the universe’s earliest years.

Comments


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Rod

June 12, 2023 at 7:55 am

Very interesting. JADES is getting interesting. The Cosmos in its Infancy: JADES Galaxy Candidates at z > 8 in GOODS-S and GOODS-N, https://arxiv.org/abs/2306.02468, 04-June-2023. "We present a catalog of 717 candidate galaxies at z>8 selected from 125 square arcminutes of NIRCam imaging as part of the JWST Advanced Deep Extragalactic Survey (JADES)."

My observation. No metal free gas or the pristine gas from postulated BBN is seen that is said to fill the early universe, dust is reported in JADES paper and more study required apparently to show metallicity. Cosmology calculators indicate light-time of some 13 Gyr or a bit more for z=8.0 and age of universe at z=8, 0.646 Gyr.

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Jon Seamans

June 12, 2023 at 5:55 pm

I'll add that the confirmed emission time for z=13.2 is about 325 Myr, not 200 Myr as posted. The earlier time applies to the highest redshift candidate(s) (not confirmed), z ~ 18.

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Brian of DRAA

June 14, 2023 at 9:25 am

that makes sense, because I found Endsley’s comment “We're not really finding evidence of these over-massive objects within our JADES sample” confusing; z= 13.2 is stated as being 200 million years after the Big Bang, while cosmologists thought the first galaxies and stars wouldn’t form until 400 million years after the Big Bang, hence any galaxy at z= 13.2 is over-massive. 325 Myr is more palatable to the Standard Model of Cosmology, but it still has galaxies forming in about 80% of the time. Where will we be if z= 18 galaxies are confirmed?

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Jon Seamans

June 14, 2023 at 11:15 pm

No doubt the trend for earlier-than-predicted galaxy evolution will remain a conundrum, maybe even for Webb. I doubt z=18 will be reached in this first serious deep-field image. Spectral confirmation with NIRSpec is needed to dust-laden low-z imposters which may be the case for here. Simplified predictions for a random distribution of galaxies across 200 arcmin^2 deep field are z~15, and calculations for non-random clustering may reduce discovery to about 30% of the time (i.e. 3 out of 10 deep-field images), https://arxiv.org/abs/2111.14865. It seems that without improved analysis algorithms, or enhancement from gravitational lensing, z =18 may not be reached. With that said, Hubble significantly exceeded post-repair/upgrade performance expectations. Maybe the same will be true for an out-of-the-box JWST 🙂

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Brian of DRAA

June 17, 2023 at 8:39 am

Jon, in the article cited by Rod (The Cosmos in its Infancy: JADES Galaxy Candidates at z > 8 in GOODS-S and GOODS-N, https://arxiv.org/abs/2306.02468, 04-June-2023) the z-photometry values were overstated, but only by z=0.25 (on avergae) so z-photometry-18 would become z-spec =17.75. My understanding is that z-spec is an acurate measurment of z, and is not corrupted by dust (as z-photo may be). I think the JADES data is for a lot of images, not just one as it took JWST 32 days of observing and JWST can do a deep field in 10 hours, so 32days x 24 hours/day / 10hours = approx 70 images. I'll read the Cornell paper.

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Brian of DRAA

June 19, 2023 at 12:53 pm

Jon, I made a mistake re the area of this 32 day survey, it was as you said, not 70 times greater as I said. I do want to "see" the distibution of these early galaxies and how they bridge the CMB map to the current galaxy distribution.

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Monica Young

June 20, 2023 at 2:25 pm

Hi Jon, I apologize for the error, and I've fixed the text above.

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Brian of DRAA

June 14, 2023 at 9:36 am

Monica, thanks for identifying JADES as the portal of JWST’s deep space data. For years I found it interesting that each month some Astronomer would declare Modified Newtonian Dynamics (MOND) is dead. The parade of celebrants at MOND's funeral reminded me of story: after being told a new book titled “100 Authors Against Einstein” was being published, Einstein replied “to defeat relativity one did not need the word of 100 scientists, just one fact”. Do these new developments mean MOND, and its ability to gather matter quickly, has returned from the dead? (see my reply to Jon S. above for details) On a different note, perhaps direct collapse of gas (and Dark Matter) into a Black Hole needs more attention too. Thanks for the intriguing article.

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Jon Seamans

June 14, 2023 at 11:29 pm

IMHO, the classic MOND concept will continue to fizzle out. Pop I star formation is the big unanswered question, and I'm tending to favor the idea that black hole seeds existed for the earliest galaxies. A direct-collapse scenario for black-hole formation falls in line with the apparent early galactic evolution we're seeing.

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Brian of DRAA

June 17, 2023 at 8:45 am

Jon, thanks for commenting. I had to look up IMHO and was disapointed it wasn't a cosmic model 🙁
Agreed, we need direct collapse Black Holes for these early galaxies to form. I'm guilty of being a cheerleader for MOND, but I think we need MOND to piece together these early galaxies so quickly (in addition to the other attributes it has over Dark Matter alone). The new cosmology may have to be lambda-CDM-MOND based on these JWST findings.
BTW - Pop 3 stars are the earliest, pure hydrogen and helium stars. 🙂

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Jon Seamans

June 18, 2023 at 10:53 pm

Brian, for some reason, I've always have trouble keeping the three star populations straight! I even looked it up before posting, but I still didn't get it right!! Do'h!!! Sometimes I just have to slow down.
Well, my last comments regarding MOND, I think it will only be an interim contribution. I'm expecting something more like Modified-ΛCDM. (DE and DM or just DE?) I'm skeptical that Newtonian dynamics will play a significant of a role in explaining the early stages of cosmic evolution. I'll just say I hope I live long enough to see a trend in the evolving theory 🙂

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Brian of DRAA

June 19, 2023 at 12:47 pm

Jon, occasionally I present at my local club and in one segment I called "Astrophysisist say the darnest things" I had the Pop 1 to pop3 stars. That says it all.
BTW - other cute astrophysics says include: lithium and all elements great than He are metals - "burn" = nuclear fusion
Keep those pop 1 stars close to you!

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