Image of the Day: Tuning in to a Spectacular Radio Halo 3.2 Billion Light Years from Earth

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The image above is part of the northern part of the galaxy cluster Abell 1758, located about 3.2 billion light years from Earth, showing the effects of a collision between two smaller galaxy clusters. Chandra X-ray data (blue) reveals hot gas in the cluster and data from the Giant Metrewave Radio Telescope (GMRT) in India (pink) shows huge "halos" generated by ultra-relativistic particles and magnetic fields over vast scales. Optical data from the Digitized Sky Survey are colored gold.

A study of this galaxy cluster and 31 others with Chandra and the GMRT shows that huge radio halos are generated during collisions between galaxy clusters. This result implies that galaxy clusters with radio halos are still forming, while clusters without this radio emission are not still accumulating large amounts of material. The result also implies that relativistic electrons are likely accelerated by turbulence generated by mergers between clusters.

The 12 million light-year wide galaxy cluster known as Abell 1758 is located 3.2 billion light years away in the constellation Canes Venatici. Clusters are groups of galaxies bound together by gravity, with swathes of hot gas permeating the intracluster medium. They are some of the largest structures in the Universe, with clumps of mysterious dark matter likely contributing to their gravitational strength.

Collisions between clusters generate huge of amounts of energy, and in this image the rich pink and blue hues represent radio and X-ray data respectively. While the X-ray data is indicative of hot gas, the GMRT data reveals radio halos generated by relativistic particles and intense magnetic fields.

The observations of Abell 1758, along with 31 other clusters in the study, show that galaxy clusters with radio halos are still forming, while clusters without clear radio emission are not still accumulating large quantities of material. The result also implies that electrons moving at close to the speed of light are likely accelerated by turbulence stirred up by the merging event.

The rate at which clusters are forming has slowly decreased over the last seven billion years due to the effects of dark energy, a force used to explain the acceleration of the expanding Universe.

Via Chandra Space Observatory

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