Science

Turbulent ‘space web’ links galaxy cluster in new radio telescope images

The new images capture radio emission from a distant cluster of galaxies in unprecedented detail, which could help shed light on the “cosmic web” of glowing hot plasma gas and magnetic fields between galaxies.

Scientists believe that the hot plasma in galaxy clusters contains bumps and turbulence that occurs when galaxies in a cluster violently merge. This turbulence imparts kinetic energy to the electrons, causing them to move at speeds approaching the speed of light – also known as relativistic speeds. When these electrons are captured by magnetic fields, the electrons are forced to move in circular paths, causing them to emit what is known as synchrotron radiation. These radio emissions should extend from the centers of the clusters for millions of light-years.

For the new images, an international team of scientists has collected observations of the galaxy cluster Abell 2255, located 1 billion light-years from Earth in the constellation Draco, by combining data from thousands of radio antennas that make up the Low Frequency Array. (LOFAR) radio telescope. They found evidence of radio synchrotron radiation distributed on a very large scale, at least 16 million light-years across.

Related: What does it look like inside a massive cluster of galaxies? The scientists used 196 lasers to find out.

For 18 nights, LOFAR focused on Abell 2255 and its 18 by 18 light-year region, which is an area of ​​the night sky roughly equivalent to the size of four full moons stacked on top of each other from our vantage point. Earth. This is the first time that astronomers have recorded radio emission from such a large area and over such a long period.

The new images of Abell 2255 are 25 times sharper than images taken with older radio telescopes and contain 60 times less noise (unwanted noise that masks the desired signal).

Composite image of the Abell 2255 galaxy cluster. ROSAT X-ray data shown in blue. They show hot gas between galaxies. Yellow and purple are radio data from LOFAR. The purple glow is the radio emission that surrounds the entire cluster. The yellow bands are fast moving particles in the cluster’s magnetic fields. The background image was captured using SSDS. (Image credit: ROSAT/LOFAR/SDSS/Botteon et al.)

Although galaxy clusters are the most densely populated regions of the universe, consisting of hundreds and thousands of galaxies, amazing physical phenomena also occur between them. Between the galaxies of galaxy clusters such as Abell 2255, there is a gas composed of high-energy particles and magnetic fields, the origin of which is unclear. How these particles and magnetic fields affect each other is also unknown.

“Based on the new images and our calculations, we think that the radio emission from Abell 2255 was generated during the formation of the cluster,” said study leader Andrea Botteon, an astrophysicist at the University of Bologna in Italy. (will open in a new tab). Botteon added that the LOFAR observations of Abell 2255 represent the first time that radio waves have been generated far from the center of a galaxy cluster.

The prevalence of radio emission indicated that shocks and turbulence in hot gas effectively transferred kinetic energy to relativistic particles and magnetic fields in a region extending to the outskirts of the cluster.

Botteon and his colleagues also put forward theories about the physical interactions that take place between the hot gas of Abell 2255 and its magnetic fields.

“In our theory, we assume that the particles are accelerated by the huge turbulence and shock that occurs when the cluster forms,” Botteon said. “In turn, these movements can also amplify magnetic fields.”

In addition to further studying Abell 2255, the team intends to direct LOFAR and other future telescopes such as the square kilometer array to other galaxy clusters. The goal will be to study these densely populated regions of space for extended periods of time to learn more about the cosmic network that connects galaxies within clusters.

The team’s study was published Nov. 2 in the journal Science Advances. (will open in a new tab).

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