Sloshing cold front detected in a massive cluster of galaxies

Analyzing data from NASA’s Chandra X-ray Observatory, astronomers from India and South Africa examined a massive cluster of galaxies known as Abell 2566. They discovered sloshing cold fronts in the intracluster medium (ICM) of this cluster. The finding was reported in a research paper published on the preprint server on May 17 arXiv.

Galaxy clusters contain thousands of galaxies that are connected by gravity. They are the largest known gravitationally bound structures in the universe, and could serve as excellent laboratories for studying the evolution and cosmology of galaxies.

In general, the so-called cold fronts are sharp discontinuities in surface brightness observed on X-rays, where the drop in surface brightness and gas density is accompanied by a jump in gas temperature, with the denser region being colder than the rarefied area. region.

Now a team of astronomers led by Sonali K. Kadam of Swami Ramanand Teerth Marathwada University in India has identified such features in Abell 2566: a cluster of galaxies with a cool core at a redshift of 0.08, with an estimated mass of about 217 trillion solar masses. .

By analyzing Chandra images and archival radio data, Kadam’s team found evidence of gas sloshing in Abell 2566’s core, along with a few cold fronts in the area.

First, the images collected revealed an unusual morphology of the ICM distribution – in the form of spiral gas sloshing around edges in the surface brightness distribution. Spectral analysis performed by the astronomers subsequently confirmed a link between these morphological discontinuities and the cold fronts.

“A detailed analysis of the sectoral brightness profiles along these edges confirms their origin as a result of gas sloshing, also called sloshing cold fronts,” the researchers explained.

Furthermore, the observations identified a shift of about 22,200 light-years between the brightest cluster galaxy (BCG) and the X-ray emission peak, as well as a close association of the BCG with a neighboring system. The paper’s authors hypothesize that this shift could have produced the sloshing structure in Abell 2566.

Based on the data collected, the astronomers assume that the observed features and the complex morphology of the plasma distribution in Abell 2566 have a common origin, as they may be the result of a small merger. The team noted that a subcluster may have disrupted the main cluster by properly shifting its gravitational potential.

“Such displacement further results in the formation of cold fronts, the concentrically shaped boundaries in the surface brightness that are produced by the gas in the core as it moves around the potential well. These cold fronts further develop spiral patterns in the plasma distribution , provided the sloshing direction is right close to the celestial plane,” the scientists concluded.

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