Chandra finds a bridge of hot gas between galactic clusters

Astronomers have found evidence of “missing” mass in the form of giant threads, or filaments, of superheated gas thanks to Chandra .


This proposed hard-to-detect matter is known as WHIM .

Astronomers have used data from NASA ‘s Chandra X-ray Observatory to identify key structures and search for “missing” matter in the Universe.

This missing material is not dark matter, which is invisible, unknown in nature and thought to make up most of the matter in the universe, but “normal” matter found in familiar objects like stars, planets and ourselves.

About a third of this matter that was created in the first billion years after the Big Bang has yet to be detected by observations of the local universe, that is, in regions less than a few billion light-years from Earth. Land

Searching for the lost matter

Scientists have proposed that at least some of this unaccounted-for mass could be hidden in filaments of warm to hot gas (temperatures of 10,000 to 10 million Kelvin) in the space between galaxies and galaxy clusters. They have called this the “warm-hot intergalactic medium” or WHIM (Warm-Hot Intergalactic Medium).

A team of astronomers examined Chandra data from Abell 98 (pictured), which is about 1.4 billion light-years from Earth, and conclude that they likely found evidence that this WHIM resides in the space between the two star clusters. galaxies. The Chandra data reveal a bridge of X-ray emission between two of the colliding clusters containing gas at a temperature of about 20 million Kelvin and relatively cooler gas at a temperature of about 10 million Kelvin. The hotter gas in the bridge is likely due to gas in the two groups that overlap each other. The temperature and density of the cooler gas are consistent with the predictions for the hotter, denser gas from the WHIM.

Additionally, the Chandra data shows the presence of a shock wave, which is similar to the sonic boom of a supersonic aircraft. The location of the shock wave is identified by sudden decreases in X-ray brightness and gas temperature, measured from the north side to the south side of the shock. This shock wave is driven and located in front of one of the galaxy clusters when it begins to collide with another cluster, the Chandra telescope reports on its website .

This would be the first time astronomers have found such a shock wave in the early stages of a galaxy cluster collision, before the cluster centers pass past each other. This shock wave may be directly related to the discovery of the WHIM in Abell 98 because it has heated the gas between the clusters as they collide. This may have raised the temperature of the gas in the WHIM filament , which is estimated to contain about 400 billion times the mass of the Sun, high enough to be detected with the Chandra data.

A paper describing this result by a team led by Arnab Sarkar, a Ph.D. candidate at the Cambridge Institute for Astronomy, was published in The Astrophysical Journal Letters . ( EuropaPress )