Long-awaited data from the James Webb Space Telescope is now allowing astronomers to peer into the past and discover galaxies from the early universe.
The results, released Monday (January 9) at the 241st meeting of the American Astronomical Society in Seattle, show how the James Webb Space Telescope (Webb or JWST) lives up to its potential — and how much more remains to be discovered.
“Now I can tell you about scientific advances and I can make these graphs, but I’m still a little dizzy because a year ago we didn’t know any of this,” Jane Rigby, astrophysicist at NASA Goddard. This was stated during the plenary report by the Space Flight Center in Maryland, which led the scientific commissioning of the observatory. “We didn’t know if the mission would be a complete failure or if it would work.”
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But now the answer is clear: the mission works. “This is nothing short of good news: the scientific requirements are met or exceeded across the board,” Rigby said. “The whole thing is so great,” she said of the mission science.
Meanwhile, the scientists shared some of the results of this work in numerous keynotes at the meeting, as well as during a press conference on Monday on JWST observations of extremely distant galaxies, which astronomers call “high redshift.”
Perhaps one of the biggest takeaways from JWST’s work to date is that by allowing astronomers to look into the past, JWST is redefining what is considered high redshift.
“What is high redshift? Well, it’s been a moving target throughout my career,” James Rhodes, an astronomer at NASA Goddard, said during a press conference. “And JWST has certainly moved the goalpost further.”
Galaxies have a wide range of morphologies.
One study analyzing JWST data looked at how galaxies change shape. The Hubble sequence classifies galaxies into three stages based on shape: spiral young galaxies, lenticular transition, and elliptical old galaxies. However, scientists are not sure which forms came into being, when, and by what processes, especially during the first 3 billion years of the universe’s existence.
“We would like to understand what the galaxies were like in even earlier times. When did these first bulges of spiral arms in galaxies actually form? This was announced to journalists at a press conference by Ceyhan Kartaltepe, an astrophysicist from the Rochester Institute of Technology. “In short, when did the Hubble sequence actually start? We don’t know that yet.”
Using JWST data collected in June 2022, Kartaltepe’s team analyzed 850 ultra-distant galaxies, classifying galaxies according to their shape into disk, spheroidal, or irregular, to mimic the Hubble sequence. The researchers also compared the JWST data with similar observations from the Hubble Space Telescope.
“The results are a bit surprising since no one really knew what we would see when we looked at these galaxies with JWST,” Kartaltepe told reporters. “From Hubble, we just didn’t see much. There were stains, if they were visible at all.”
Hubble was able to classify about 45% of the galaxies it saw as disks, but most of the targets were unclassifiable or unresolved. “They were too dim or too small for us to see anything,” Kartaltepe said.
The same classification with JWST data showed that galaxies with disks make up as much as 60%. The increase is due to the observatory’s ability to explore space at a higher resolution, Kartaltepe said: JWST data showed sharper features in galaxies and more.
“We see a wide variety of morphologies in galaxies up to the highest redshifts that we have been able to study,” Kartaltepe said, referring to the most distant objects observed to date. As the universe is constantly expanding, light waves from very distant objects are stretched out, moving them towards the redder side of the electromagnetic spectrum.
Although the researchers knew that some galaxies with such high redshifts must have disks, they were surprised to see so many disk-shaped galaxies. Future observations will help scientists better understand the structure and evolution of galaxies.
“We can really start looking at samples of thousands of galaxies at these redshifts and really start to quantify when the first disks and bulges were able to form in our universe,” Kartaltepe said.
Discovery of the youngest galaxies (chemically)
Another new study analyzing early JWST observations looked at the three redshift 8 galaxies we see as they were over 13 billion years ago to better understand their composition and temperature.
“We have detected what is possibly the most chemically primitive galaxy among the first three spectra of cosmic dawn galaxies from the JWST,” said Rhodes, the project’s lead investigator.
Rhoads and colleagues found the presence of a very small amount of oxygen, only 2% of what is in the Milky Way, and this is one of the lowest oxygen abundances measured in galaxies to date. The scientists also found a lot of hydrogen, suggesting that these galaxies are very young, and determined that the gas in these galaxies is very hot, perhaps twice the temperature of similar gas in the Milky Way.
Rhoads said these galaxies are “quite small” and contain effectively young stars. In addition, most of the light came from glowing gas clouds, not from the surfaces of stars. These properties are also possessed by the so-called “Green Pea” galaxies, which, according to astronomers, are good analogues of the galaxies of the early Universe.
“They are unusual, they are interesting, they are very interesting to study,” Rhoads told reporters at a conference on the Green Pea galaxies. “And in the neighboring universe, they are quite rare.”
A Deeper Look at the Shock Wave Through Stefan’s Quintet
In other results presented today, the researchers showed how the galactic shock wave affected warm and cold hydrogen gas in the Stefan quintet.
The intruder galaxy crashes into Stefan’s quintet at 435 to 620 miles (700 to 1,000 kilometers) per second, causing a shockwave that travels through the group at faster than the speed of sound. However, a previous study using NASA’s now-retired Spitzer Space Telescope showed a huge number of “very fragile” hydrogen molecules in the neighborhood, and how these molecules survived the “powerful energy” of the impact remained a mystery, Philip Appleton, senior scientist from the California Institute of Technology’s (IPAC) Infrared Processing and Analysis Center and the project’s lead investigator, said during a press conference.
A possible explanation, according to Appleton, is that the shock wave hit a lumpy patch of cold interstellar medium that took the brunt of the hot gas behind the impact, breaking the cloud into tiny clouds.
“These new observations gave us some answers, but ultimately showed how much we still don’t know,” Appleton said in a statement. “Essentially, we have one side of the story. Now it’s time to get to know another.”
Large number of higher redshift candidate galaxies discovered
The JWST has allowed astronomers to go far beyond the capabilities of Hubble, as evidenced by the numerous ultra-long-range candidate galaxies discovered by the JWST. In some of these observations, the researchers searched for and found numerous galaxies with redshifts greater than 11 that appear 200 to 400 million years after the Big Bang.
As usual when evaluating candidates, some of the 87 identified candidates may turn out to be fakes in the course of further spectroscopic observations. However, even if scientists can only confirm a small fraction of the findings, our “previous picture of galaxy formation in the early universe needs to be revised,” said Haojing Yang, an astronomer at the University of Missouri-Columbia and lead author of the study. during a press conference.
The role of black holes in the evolution of galaxies
JWST also helps astronomers look into the centers of nearby galaxies. For example, the researchers looked at the galaxy NGC 7469, which contains an active supermassive black hole at its center and is surrounded by a ring of intense star formation.
“This is the perfect laboratory for us to understand whether black holes really affect the stellar and gaseous composition of the host galaxy, and if so, in what way,” Vivian Wu, study lead researcher and University of California astronomer, said during the news. Irvine. the conference.
While Hubble’s observations of NGC 7469 have shown that dark dust obscures visible light from stars, Wu said that thanks to infrared vision, JWST “represents a much smoother version of the light profile now that dust is no longer in the way.”
The team also discovered a very young star forming region that was previously obscured by dust, Wu said.
Detailed new information about the galaxy gives a clearer picture of the distribution of various gases at different temperatures. Using this information, the team found that the supermassive black hole at the center of the galaxy drives fast, highly ionized winds that send shockwaves into the surrounding interstellar medium.
“This gives us direct evidence that the supermassive black hole at the center of this galaxy is blowing winds at us,” said W.[ing] us to understand how black holes and galaxies evolve together.”
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