Astronomers from India and South Africa have made significant strides in understanding the massive galaxy cluster known as Abell 2566 through data analysis from NASA's Chandra X-ray Observatory. Their research, reported in a paper published on May 17 on the preprint server arXiv, reveals the presence of sloshing cold fronts within the intracluster medium (ICM) of this cluster.
Galaxy clusters, the universe's largest gravitationally bound structures, consist of up to thousands of galaxies. These clusters serve as crucial laboratories for studying galaxy evolution and cosmology due to their vast size and complexity. Cold fronts, characterized by sharp surface brightness discontinuities in X-ray images, are particularly intriguing. These features show a drop in surface brightness and gas density, coupled with a temperature increase, where the denser region remains cooler than the surrounding area.
Led by Sonali K. Kadam of Swami Ramanand Teerth Marathwada University in India, the team focused on Abell 2566, a cool core galaxy cluster at a redshift of 0.08. This cluster has an estimated mass of approximately 217 trillion solar masses. Using Chandra images and archival radio data, Kadam's team discovered gas sloshing in the cluster's core and identified a pair of cold fronts within its environment.
The collected images revealed an unusual morphology in the ICM distribution, showcasing spiral-shaped gas sloshing and edges in surface brightness distribution. Spectral analysis confirmed these morphological discontinuities' association with cold fronts. “A detailed analysis of the sectorial brightness profiles along these edges confirm their origin due to sloshing of gas, referred to as the sloshing cold fronts,” the researchers explained.
Additionally, the observations highlighted an offset of about 22,200 light-years between the brightest cluster galaxy (BCG) and the X-ray emission peak, alongside a close association of the BCG with a neighboring system. The team hypothesizes that this offset might have caused the sloshing structure observed in Abell 2566.
From the gathered data, the astronomers suggest that the observed features and complex plasma distribution morphology in Abell 2566 likely share a common origin—potentially due to a minor merger. They propose that a sub-cluster may have disturbed the main cluster by displacing its gravitational potential well. “Such a displacement further results in the formation of cold fronts, the concentrically shaped borders in the surface brightness produced by the core's gas as it moves around the potential well. These cold fronts further develop spiral patterns in the plasma distribution provided the sloshing direction is close to the plane of sky,” the scientists concluded.
This research provides valuable insights into the dynamic processes within galaxy clusters, enhancing our understanding of their evolution and the role of minor mergers in shaping their structure.