Astronomers have observed a burning gas cloud surrounding a protogalaxy cluster

Astronomers have observed a burning gas cloud surrounding a protogalaxy cluster

The simulation depicts the large-scale heating scenario around the proto-cluster, using data from supercomputer simulations. This is thought to be a similar scenario to what was observed in a COSTCO-I primer. The yellow region in the center of the image represents a huge, hot gas mass several million light-years across. Blue indicates cooler gas present in the outer regions of the protocluster and filaments connecting the hot gas to other structures. The white dots included in the gas distribution are the light emitted by stars. Credit: The Three Hundred Collaboration

Astrophysicists using the WM Keck Observatory in Maunakea, Hawaii, have discovered a proto-galaxy cluster in the early universe surrounded by surprisingly hot gas.

This scorching gas embraces a region of a giant cluster of galaxies called COSTCO-I. Observed when the universe was 11 billion years younger, COSTCO-I dates back to a time when the gas that filled most of the space outside of visible galaxies, called medium between galaxies, it was noticeably cooler. During this era, known as “Cosmic Noon,” galaxies in the universe were at the peak of star formation. Their stable environment was full of cold gas They needed to form and grow, with temperatures around 10,000 degrees Celsius.

In contrast, the gas boiler associated with COSTCO-I appears ahead of its time, roasted in a hot, complex state; Temperatures are similar to the current galactic medium, which ranges from 100,000 to more than 10 million degrees Celsius, and is often called the “Warm Intergalactic Mean” (WHIM).

The discovery marks the first time astrophysicists have identified a patch of ancient gas that exhibits characteristics of the modern galactic medium. It is by far the oldest known part of the universe that has been boiled down to today’s WHIM temperatures.

The research, which is led by a team from the Kavli Institute for Physics and Mathematics of the Universe (Kavli IPMU, part of the University of Tokyo), is published in Astrophysical Journal Letters.

“If we think of the present galactic medium as a giant cosmic stew simmering and frothing, COSTCO-I was likely the first bubble that astronomers noticed, during an era in the distant past when most of the pot was still boiling,” said Khee-Gan Lee, associate professor at Kavli IPMU and co-author of the paper.

Astronomers have observed a burning gas cloud surrounding a protogalaxy cluster

This figure compares the absorption of hydrogen observed near the protocluster COSTCO-I (upper panel), to the absorption expected due to the presence of the protocluster as calculated from computer simulations. Strong hydrogen absorption is shown in red, weak absorption in blue, and intermediate absorption in green or yellow. The black dots in the figure show where astronomers have detected galaxies in that region. At COSTCO-I (with its center marked as a star in both plates), astronomers found that the observed hydrogen uptake was not very different from the average value of the universe for that era. This is surprising because one would expect to find extended absorption of hydrogen spanning millions of light-years in that region consistent with the observed high concentration of galaxies. This figure is adapted from Dong et al. 2023 Astrophysical Journal Letters condition. Credit: Dong et al.

The COSTCO-I team observed it when the universe was only a quarter of its current age. galaxy protocolcluster Its total mass is more than 400 trillion times that of our Sun and it 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 the Keck Observatory’s Low Resolution Imaging Spectroradiometer (LRIS). The large mass and size of galaxy clusters usually cast a shadow when seen at wavelengths of neutral hydrogen associated with protocluster gas.

This absorption shadow is not found at COSTCO-I.

“We were surprised because hydrogen absorption is one of the common ways to search for protoclusters, and other protoclusters near COSTCO-I also show this absorption signal,” said Chenzi Dong, a master’s degree student at the University of Tokyo and lead author of the book. the study. “The ultraviolet-sensitive capabilities of LRIS on the Keck I telescope allowed us to make maps of hydrogen gas with such high confidence that the COSTCO-I signature simply wasn’t there.”

absence neutral hydrogen Tracking the proto-cluster indicates that the gas in the proto-cluster must have been heated to a temperature of perhaps a million degrees, well above the expected cold state of the galactic medium in that distant era.

“The properties and origin of WHIM remain one of the biggest questions in astrophysics right now. To be able to glimpse one of WHIM’s early heating sites will help reveal the mechanisms that caused the boiling of intergalactic gas in present-day foaming,” he said. for me. “There are a few possibilities for how this might have happened, but it could be either because the gas is heating up as they collide with each other during Gravity collapseor perhaps giant radio jets pumping energy from the supermassive black holes inside the protocluster.”

The intergalactic medium acts as a reservoir of gas feeding raw materials into the galaxies. Hot gas behaves differently than cold gas, which determines how easy it is to flow into it galaxies to form stars. As such, having the ability to study WHIM’s growth in early universe Astronomers have been able to form a coherent picture of the formation of galaxies and the life cycle of the gas that feeds them.

more information:
Chenze Dong et al, Observational evidence for large-scale heating of gas in a protogalactic cluster at z = 2.30, Astrophysical Journal Letters (2023). DOI: 10.3847/2041-8213/acba89

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