Los galaxy clusters They are some of the largest known objects in the universe and, as the name suggests, are home to a large number of galaxies, sometimes even thousands. Between them extends the call intracumulus medium (ICM).for its acronym in English) of gas, which expands beyond the galaxies themselves.
Much of the physics of galaxy clusters is well known; however, observations of the early phases of ICM formation remain scarce. Previously, it had only been studied in fully formed nearby galaxy clusters.
A large reservoir of hot gas has been detected in the still-forming cluster of galaxies around the Spider Web galaxy.
The detection of ICM in protocumulus (ie clusters of galaxies still in formation) located at a great distance, would allow the astronomical community to capture these clusters in the early stages of formation. A team led by Luke DiMascoloresearcher at the University of Trieste (Italy) and first author of a study published this week in Naturesought to detect this medium introcluster in a protocluster of the early stages of the universe.
Galaxy clusters are so massive that they can gather gas that heats up as it falls toward the cluster. “Cosmological simulations have been predicting the presence of hot gas in protocumulus for more than a decade, but observational confirmations were lacking,” he explains. Elena Rasiaa researcher at the Italian National Institute for Astrophysics (INAF) in Trieste, Italy, and co-author of the study, “The search for a key observational confirmation led us to carefully select one of the most promising candidate protocumulus.”
The study has focused on the Spider Web protocluster, located at a time when the universe was only 3 billion years old.
It was about the web protoclusterlocated in a time when the universe was only 3 billion years old and named for being around the Spider Web galaxy (formally known as MRC 1138-262).
Despite being the most studied protocumulus, the detection of the ICM had been unsuccessful. Finding a large reservoir of hot gas in this protocluster would indicate that the system is on the way to becoming a long-lasting and stable cluster of galaxies rather than dispersing.
The Sunyaev-Zeldovich thermal effect
Di Mascolo’s team detected the ICM of the Cobweb protocluster through what is known as the Sunyaev-Zeldovich (SZ) thermal effect. This effect occurs when light from microwave cosmic background (the radiation left over from the Big Bang), passes through the ICM.
When this light interacts with fast-moving electrons in the hot gas, it gains a bit of energy and its color, or wavelength, changes slightly. “At the right wavelengths, the SZ effect appears as a shadow effect of a galaxy cluster on the cosmic microwave background,” explains Di Mascolo.
By measuring these shadows in the cosmic microwave background, the astronomical community can infer the existence of the hot gas, estimate its mass, and map its shape. “Today, thanks to its unmatched resolution and sensitivity, ALMA it is the only facility capable of making such a measurement of the distant progenitors of massive clusters,” says Di Mascolo. The Atacama Large Millimeter/submillimeter Array (ALMA) is operated by the European Southern Observatory (ESO) and other institutions in Chile.
They determined that the Cobweb Protocluster contains a vast reserve of hot gas at a temperature of a few tens of millions of degrees Celsius. Cold gas had previously been detected in this protocluster, but the mass of the hot gas found in this new study exceeds it by thousands of times.
This finding shows that the Cobweb Protocluster is on track to become a massive galaxy cluster in around 10 billion years, increasing its mass by at least a factor of ten.
This finding shows that the Cobweb Protocluster is on track to become a massive galaxy cluster in about 10 billion years.
Tony Mroczkowskia co-author of the paper and an ESO researcher, explains that “this system presents enormous contrasts. The hot thermal component will destroy much of the cold component as the system evolves, and we are witnessing a delicate transition.”
It concludes by stating that it “provides observational confirmation of long-held theoretical predictions about the formation of the largest gravitationally bound objects in the universe.”
These results help lay the groundwork for synergies between ALMA and ESO’s forthcoming Extremely Large Telescope (ELT), which will “revolutionize the study of structures like this,” he says. Mario Noninoco-author of the study and researcher at the Trieste Astronomical Observatory.
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