Astronomers catch hot birth of galaxy cluster more than 11 billion light-years away

Astronomers have detected an enormous cloud of gas tens of millions of degrees hot surrounding a quasar in a galaxy cluster more than 11 billion light-years away. The study, published in Astronomy & Astrophysics, offers the clearest view yet of a nascent galaxy cluster in the early universe. Using 634,000 seconds of Chandra X-ray Observatory data, the team found diffuse, extended X-ray emission around a quasar, confirming the presence of a hot, ionized gas component. The gas, called proto-ICM, is in the early stages of forming, and its detection is significant as it shows the first evidence of thermal emission from such a structure at redshift z > 3.

The study involved a team led by Andrea Travascio, who analyzed a protocluster centered on a quasar at redshift z = 3.25, when the universe was less than 2 billion years old. The team ruled out contamination from the quasar's light and confirmed the presence of a hot gas component. The X-ray emission extended to at least 98,000 light-years from the quasar, and the gas temperature was estimated to be around 21 million Kelvin. The gas has a mass of about 2.6 trillion times the sun's mass and accounts for 56% of the normal matter in the cluster. This is a significant result because it shows the early-universe structure has reached a share of hot gas comparable to mature clusters, even though the universe was less than 2 billion years old.

The findings suggest that the hot gas in the proto-ICM is physically distinct from the cooler gas cloud around the quasar. The study highlights the importance of future observations with more sensitive telescopes to confirm and refine these results. The research is based on a combination of observational data and simulations, and the team emphasizes that the reported quantities are rough estimates with large uncertainties due to the limited number of detected thermal photons.

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