Using the James Webb Space Telescope (JWST), researchers from Canada’s NIRISS Unbiased Cluster Survey (CANUCS) team have identified the most distant globular clusters ever discovered. These dense groups of millions of stars may be remnants containing the first and oldest stars in the universe.
Early analysis of Webb’s First Deep Field image, which depicts some of the universe’s earliest galaxies, was published today in The Astrophysical Journal Letters.
“JWST was built to find the first stars and galaxies and help us understand the origins of complexity in the universe, such as the chemical elements and the building blocks of life,” said Lamiya Mowla, Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto and co-lead author of the study. “This discovery in Webb’s First Deep Field already provides a detailed picture of the earliest phase of star formation, confirming the incredible power of JWST.”
In the finely detailed Webb’s First Deep Field image, the researchers focused on what they’ve dubbed “the Sparkler galaxy,” located nine billion light-years away. This galaxy gets its name from the compact objects that appear as tiny yellow-red dots around it, referred to as “sparkles” by the researchers. The team suggested that these sparks could be either young star clusters actively forming stars — born three billion years after the Big Bang at the peak of star formation — or old globular clusters. Globular clusters are ancient collections of stars from a galaxy’s childhood and contain clues about the earliest stages of formation and growth.
From their initial analysis of 12 of these compact objects, the researchers determined that five of them are not only globular clusters, but are also among the oldest known.
“Watching the first images of JWST and discovering ancient globular clusters around distant galaxies was an incredible moment, one that was not possible with previous Hubble Space Telescope imaging,” said Kartheik G. Iyer, Dunlap Fellow at the Dunlap Institute. for Astronomy & Astrophysics at the University of Toronto and co-lead author of the study. “Because we were able to observe the glare over a range of wavelengths, we were able to model them and better understand their physical properties, such as how old they are and how many stars they contain. We hope that the knowledge that globular clusters can be observed from such great distances with JWST will stimulate further science and searches for similar objects.”
The Milky Way galaxy has about 150 globular clusters, and exactly how and when these dense clumps of stars formed is not well understood. Astronomers know that globular clusters can be extremely old, but it is incredibly challenging to measure their age. Using very distant globular clusters to age the first stars in distant galaxies has not been done before and is only possible with JWST.
“These newly identified clusters formed close to the first time it was even possible to form stars,” Mowla says. “Because the Sparkler galaxy is much further away than our own Milky Way, it is easier to determine the age of its globular clusters. We observe the Sparkler as it was nine billion years ago, when the universe was only four-and-one – half a billion years old, looking at something that happened a long time ago. Think of it like guessing a person’s age based on their appearance – it’s easy to tell the difference between a 5 and a 10 year-old, but hard to tell the difference between a 50-year-old and a 55-year-old.”
Until now, astronomers could not see the surrounding compact objects of the Sparkler galaxy with the Hubble Space Telescope (HST). This changed with the increased resolution and sensitivity of JWST, revealing for the first time the tiny dots around the galaxy in Webb’s First Deep Field image. The Sparkler galaxy is special in that it is magnified by a factor of 100 due to an effect called gravitational lensing — where the SMACS 0723 galaxy in the foreground distorts what’s behind it, much like a giant magnifying glass. In addition, gravitational lensing produces three separate images of the Sparkler, allowing astronomers to study the galaxy in greater detail.
“Our study of the Sparkler highlights the tremendous power in combining the unique capabilities of JWST with the natural magnification provided by gravitational lenses,” said Chris Willott, head of the CANUCS team at the Herzberg Astronomy and Astrophysics Research Center at the University of Groningen. National Research Council. “The team is excited about more discoveries to come next month as JWST sets its eye on the CANUCS galaxy clusters.”
The researchers combined new data from JWST’s Near-Infrared Camera (NIRCam) with HST archive data. NIRCam detects faint objects with longer and redder wavelengths to observe beyond what is visible to the human eye and even HST. Both magnifications resulting from the galaxy cluster’s lensing and the high resolution of JWST have made it possible to observe compact objects.
The Canadian-made Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST provided independent confirmation that the objects are ancient globular clusters because the researchers did not observe oxygen emission lines — emissions with measurable spectra given off by young clusters that are active. form stars. NIRISS also helped unravel the geometry of the Sparkler’s triple-lens images.
“JWST’s made-in-Canada NIRISS instrument was vital in helping us understand how the three images of the Sparkler and its globular clusters are connected,” said Marcin Sawicki, Canada Research Chair in Astronomy, professor at Saint Mary’s University and co-author of the study. “When we saw several Sparkler globular clusters three times, it became clear that they revolve around the Sparkler galaxy rather than just happen to be in front of it.”
JWST will observe the CANUCS fields from October 2022, using JWST data to investigate five massive galaxy clusters, around which the researchers expect to find more such systems. Future studies will also model the galaxy cluster to understand the lens effect and perform more robust analyzes to explain the history of star formation.
Collaborating institutions include York University and institutions in the United States and Europe. The research was supported by the Canadian Space Agency and the Natural Sciences and Engineering Research Council of Canada.
Hubble captures a starry sky
The Sparkler: Evolved candidates for high redshift globular clusters, captured by JWST, The astrophysical journal letters (2022). DOI: 10.3847/2041-8213/ac90ca
Quote: Webb reveals a galaxy that sparkles with the universe’s oldest star clusters (2022, September 29) retrieved September 29, 2022 from https://phys.org/news/2022-09-webb-reveals-galaxy-universe-oldest. html
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