May 28, 2023


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The first bubble in the intergalactic soup | Urania

A team of astrophysicists has discovered a proto-cluster of galaxies in the early universe surrounded by surprisingly hot gas.

This scorching gas covers a region of a giant cluster of galaxies called COSTCO-I. Observed when the universe was younger than 11 billion years ago, COSTCO-I comes from a time when gas filled most of the space outside of visible galaxies, called the intergalactic medium, and was much cooler. During this era, known as “cosmic noon,” galaxies in the universe were at the peak of star formation. Their stable environment was filled with the cold gas they need to form and grow, and the temperatures were around 10,000on c

In contrast, the gas boiler associated with COSTCO-I appears ahead of its time, burning hot and complex; Temperatures are similar to the current galactic medium, which ranges from 100,000 to 10 million degrees Celsius, and is often referred to as a warm, warm intergalactic medium (WHIM).

The discovery is the first time astrophysicists have identified a patch of ancient gas that exhibits characteristics of the modern galactic medium. This is by far the oldest known part of the universe to reach today’s WHIM temperature.

The research, led by a team at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, part of the University of Tokyo), was published March 14, 2023 in Astrophysical Journal Letters.

If we think of the intergalactic medium today as a giant cosmic stew simmering and accumulating, COSTCO-I was likely the first bubble observed by astronomers during an era in the distant past when most of the pot was still cold said Khee-Gan Lee, assistant professor at Kavli IPMU and co-author of the paper.

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The COSTCO-I team observed it when the universe was only a quarter of its current age. The protogalaxy cluster has a total mass of over 400 trillion solar masses and spans several million light years.

While astronomers now regularly spot such distant galaxy clusters, the team found something strange when they examined the ultraviolet spectra covering the COSTCO-I region using low resolution imaging spectrometer (LRIS) Keck Observatory. Under normal circumstances, the great mass and size of primary galaxy clusters would cast shadows at their characteristic wavelengths. neutral hydrogenassociated with the primary cluster gas.

No absorption shadow was found at the COSTCO-I site.

We were surprised because hydrogen absorption is a common way to search for protoclusters, and other protoclusters near COSTCO-I show this absorption signal. said a graduate student at the University of Tokyo and lead author of the study. LRIS’ ultraviolet-sensitive capabilities allowed us to confidently map hydrogen gas, a COSTCO-I signature not present.

The lack of neutral hydrogen in the protocluster means that the gas inside must have been heated to a temperature of perhaps a million degrees, far above the expected coldness of the galactic medium in that distant era.

The properties and origin of WHIMs remain one of the biggest questions in astrophysics today. Being able to look at one of WHIM’s former heating sites will help reveal the mechanisms that caused the boiling of intergalactic gas in the current foam. He said to me. There are several possibilities as to how this could happen, but it could either be because the gas is heating up as it collides with itself during gravitational collapse, or giant radio jets could be pumping energy out of supermassive black holes within the primary block.

The intergalactic medium serves as a reservoir of gas, which supplies raw materials to it galaxies. Hot gas behaves differently than cold gas, which determines how easily it flows into galaxies to form stars. Therefore, by being able to directly study WHIM growth in the early universe, astronomers can build a coherent picture of galaxy formation and the life cycle of the gas that moves them.

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Agnes Nowak

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Source: Kik Observatory

Pictured: A simulated visualization shows a large-scale heating scenario around a proto-cluster of galaxies using data from supercomputer simulations. Source: The Three Hundred Collaboration