NASA’s Chandra finds galaxy cluster collision on a ‘WHIM’

Astronomers taking stock of the fabric within the native universe hold developing quick. A brand new consequence from NASA’s Chandra X-ray Observatory a couple of system of colliding galaxy clusters might assist clarify this shortfall.

Though scientists know an ideal deal in regards to the composition of the universe, there was a vexing drawback they’ve struggled to clarify—there’s a vital quantity of matter that has not but been accounted for.

This lacking mass isn’t the invisible dark matter, which makes up a majority of the matter within the universe. It is a separate puzzle the place a couple of third of the “regular” matter that was created within the first billion years or so after the big bang has but to be detected by observations of the local universe, that’s, in areas lower than a couple of billion light-years from Earth. This matter is made up of hydrogen, helium, and different components and makes up objects like stars, planets, and people.

Scientists have proposed that at the very least a few of this lacking mass may very well be hidden in gigantic strands, or filaments, of heat to sizzling (temperatures of 10,000 to 10,000,000 kelvins) gasoline within the space in between galaxies and clusters of galaxies. They’ve dubbed this the “warm-hot intergalactic medium,” or WHIM.

A staff of astronomers utilizing Chandra to watch a system of colliding galaxy clusters has probably discovered proof of this WHIM residing within the space between them.

“Discovering these filaments of lacking matter has confirmed to be exceptionally tough, and just a few examples are identified,” stated Arnab Sarkar of the Middle for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, who led this examine. “We’re excited that we now have probably pinpointed one other.”

The researchers used Chandra to review Abell 98, which comprises colliding galaxy clusters about 1.4 billion light-years from Earth. The Chandra information reveals a bridge of X-ray emission between two of the colliding clusters containing gasoline at a temperature of about 20 million kelvins and cooler gasoline with a temperature of about 10 million kelvins. The warmer gasoline within the bridge is probably going from gasoline within the two clusters overlapping with one another. The temperature and density of the cooler gasoline agree with predictions for the most well liked and densest gasoline within the WHIM.

As well as, the Chandra information exhibits the presence of a shock wave, which has similarities to a sonic increase from a supersonic airplane. This shock wave is pushed by and situated forward of one of many galaxy clusters as it’s beginning to collide with one other cluster. That is the primary time astronomers have discovered such a shock wave within the early levels of a galaxy cluster collision, earlier than the facilities of the cluster cross by each other.

“We expect this shock wave is a vital discovery as a result of our fashions have predicted such options ought to be there, however we’ve not seen one till now,” stated co creator Scott Randall, additionally of CfA. “They seem to be a key a part of the early collision course of that can finally result in a merger of the clusters.”

This shock wave could also be instantly linked to the invention of the WHIM in Abell 98 as a result of it has heated the gasoline in between the clusters as they collide. This may occasionally have raised the temperature of the gasoline within the WHIM filament—estimated to include some 400 billion instances the mass of the Solar—excessive sufficient to be detected with Chandra information.

Galaxy clusters—which include 1000’s of galaxies, enormous quantities of sizzling gasoline, and massive reservoirs of darkish matter—are the most important constructions within the universe held collectively by gravity. Scientists assume they’re able to attain their colossal measurement by merging with each other over thousands and thousands or billions of years.

“When galaxy clusters collide, we get an opportunity to see excessive physics that we not often see in every other cosmic setting,” stated Yuanyuan Su, a co-author from the College of Kentucky.

A paper describing this consequence by Sarkar et al was printed in The Astrophysical Journal Letters