Astronomers using data from NASA’s Chandra X-ray Observatory have determined that a massive group of galaxies called Abell 1033 is actually two galaxy clusters in the process of colliding.
This composite image shows Abell 1033, two merging galaxy clusters located about 1.6 billion light-years from Earth. Image credit: X-ray – NASA / CXC / Leiden University / F. de Gasperin et al; optical – SDSS; radio – LOFAR / ASTRON / NCRA / TIFR / GMRT.
Galaxy clusters are cosmic structures containing hundreds or even thousands of galaxies. Multi-million-degree gas fills the space in between the individual galaxies. The mass of the hot gas is about six times greater than that of all the galaxies combined.
This superheated gas is invisible to optical telescopes, but shines brightly in X-rays, so an X-ray telescope like Chandra is required to study it.
By combining X-rays with other types of light, such as radio waves, a more complete picture of these important cosmic objects can be obtained.
Using X-ray and radio data, a team of astronomers led by Leiden Observatory’s Dr. Francesco de Gasperin determined that Abell 1033 is a merger of two galaxy clusters.
This extraordinarily energetic event produced turbulence and shock waves, similar to sonic booms produced by a plane moving faster than the speed of sound.
The collision interacted with another energetic cosmic process — the production of jets of high-speed particles by matter spiraling into a supermassive black hole, in this case one located in a galaxy in one of the clusters.
“These jets are revealed by radio emission to the left and right sides of the image,” the scientists explained.
“The radio emission is produced by electrons spiraling around magnetic field lines, a process called synchrotron emission.”
“The electrons in the jets are traveling at very close to the speed of light.”
“As the galaxy and its black hole moved toward the lower part of the image, the jet on the right slowed down as it crashed into hot gas in the other galaxy cluster.”
“The jet on the left did not slow down because it encountered much less hot gas, giving a warped appearance for the jets, rather than the straight line that is typically seen.”
The study shows that the energy of the electrons in the central part of the image is higher than that found in the left part. This suggests that the electrons have been reenergized, presumably when the jets interact with turbulence or shock waves in the hot gas.
The energetic electrons producing the radio emission will normally lose substantial amounts of energy over tens to hundreds of millions of years as they radiate.
The radio emission would then become undetectable. However, the vastly extended radio emission observed in Abell 1033, extending over about 500,000 light-years, implies that energetic electrons are present in larger quantities and with higher energies than previously thought.
The findings were published in the journal Science Advances.
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Francesco de Gasperin et al. 2017. Gentle reenergization of electrons in merging galaxy clusters. Science Advances 3 (10): e1701634; doi: 10.1126/sciadv.1701634
