The location of a large amount of missing matter has been revealed by a collision of some of the most massive structures in space.
In the galaxy cluster Abell 98 – in which two sub-clusters are in the process of merging – scientists have found a filament of gas consistent with something called the warm-hot intergalactic medium (WHIM).
This fog of plasma is thought to float between galaxies. It’s one of the top candidates to find the source of a shortage in visible, garden-variety particles called “baryonic matter”, which was measured in the local Universe.
Although there is evidence that the WHIM exists, it has been difficult to find enough material to support the claim that it contributes to missing baryons.
“Finding these filaments has been extremely difficult and only a few examples of it are known.” Arnab Sarkar, astrophysicistHarvard-Smithsonian Center for Astrophysics, (CfA). “We are delighted that we have likely identified another.”
The mystery of missing matter is one the strangest questions we have about our Universe. We have a good idea of the distribution of energy and matter throughout the universe. It is mostly stuff we cannot detect so don’t know what it’s like. dark energyAnd 27 percent as dark matter.
Baryonic matter is the remaining 5 to 10%. It’s the stuff we can see and detect. Black holes, humans.
We know how much baryonic material was available at the time of the event. Big BangBecause we still have radiation from that epoch Cosmic Microwave Background(CMB), which scientists were able to decode.
Scientists began to look at the baryonic matter immediately around us, but the numbers didn’t add up. There is a lot of missing information, about half to a third of the predictions made based on CMB.
One location that could be used is the “WHIM”, which can be described as filaments made of gas with temperatures between 10,000 to 10 million Kelvin. In these baryons, they are both shock-heated & compressed. It was difficult to locate these fragile structures between brighter galaxies.
Enter Abell 98. It is a cluster of galaxies located around 1.4 million light-years from Earth. Abell 98 has been observed with X-rays and revealed two hot gas structures. Sarkar and his collaborators published earlier this year an analysis that found this filament contained a Massive shock waveAs the sub-clusters are combined.
They also looked at the properties and temperature of the filament of gases. They found two distinct temperatures: one at 20,000,000 Kelvin and the other at 10,000,000 Kelvin. Researchers believe that the hotter gas is due to the gas haloes surrounding the sub-clusters.
The team discovered that the cooler gas was consistent with the hotter and denser end the theorized WHIM range.
A second paper was written by Gabriella Alvarez, an astrophysicist at CfA. This team found additional evidence for WHIM in the distance of the sub-cluster. It is far away from the shock front. This too was consistent with denser WHIM.
“These measurements,” Researchers write in the paper“Tabulating evidence” for the existence of a larger-scale structure is provided by the diffuse WHIM linking to the cluster outskirts via cosmic filaments.
We have not yet identified enough WHIM to account all the missing baryons. It could also be hiding elsewhere; evidence suggests that they may be hiding under gas filaments. Between galaxiesOr lurking in clouds of thin gas Intergalactic Space.
With new-generation Xray telescopes, our tools for detecting WHIM are becoming more powerful. They should be able to see deeper into deep space and reveal more secrets as they look between the stars.
Both papers will appear in The Astrophysical Journal LettersAnd The Astrophysical JournalThey are also available on arXiv. You can find them here HereAnd Here.
