ALMA: The Birth of a Cluster of Galaxies from the Early Universe

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ALMA: The Birth of a Cluster of Galaxies from the Early Universe

Post by bystander » Thu Mar 30, 2023 10:15 am

The Birth of a Very Distant Cluster of
Galaxies from the Early Universe

ALMA | ESO | 2023 Mar 29
Click to view full size image 1 or image 2
The Spiderweb Protocluster (with Sunyaev-Zeldovich Effect)
Image Credit: ESO/Di Mascolo et al.; HST: H. Ford

Using the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, astronomers have discovered a large reservoir of hot gas in the still-forming galaxy cluster around the Spiderweb galaxy — the most distant detection of such hot gas yet. Galaxy clusters are some of the largest objects known in the Universe and this result ... further reveals just how early these structures begin to form.

Galaxy clusters, as the name suggests, host a large number of galaxies — sometimes even thousands. They also contain a vast “intracluster medium” (ICM) of gas that permeates the space between the galaxies in the cluster. This gas in fact considerably outweighs the galaxies themselves. Much of the physics of galaxy clusters is well understood; however, observations of the earliest phases of formation of the ICM remain scarce.

Previously, the ICM had only been studied in fully-formed nearby galaxy clusters. Detecting the ICM in distant protoclusters — that is, still-forming galaxy clusters – would allow astronomers to catch these clusters in the early stages of formation. A team led by Luca Di Mascolo ... were keen to detect the ICM in a protocluster from the early stages of the Universe. ...

Di Mascolo’s team detected the ICM of the Spiderweb protocluster through what’s known as the thermal Sunyaev-Zeldovich (SZ) effect. This effect happens when light from the cosmic microwave background — the relic radiation from the Big Bang — passes through the ICM. When this light interacts with the fast-moving electrons in the hot gas it gains a bit of energy and its colour, or wavelength, changes slightly. ...

Forming intracluster gas in a galaxy protocluster at a redshift of 2.16 ~ Luca Di Mascolo et al
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