Two large cold edges have been discovered in the galaxy cluster Abell 3558

Astronomers at the University of Alabama in Huntsville have been investigating the galaxy cluster Abell 3558 using ESA’s XMM-Newton spacecraft. In their findings, they identified two major cold fronts at the edge of this group. The findings were reported in a paper published on August 30 in the print server arXiv.

Galaxy clusters contain up to thousands of galaxies bound together by gravity. They are the largest gravitationally bound structures in the universe, and can serve as excellent laboratories for studying galactic evolution and cosmology.

At a redshift of 0.048, Abell 3558 is one of the Abell 3558 clusters in the Shapley Supercluster. It has a mass of about 980 billion solar masses and a light radius of about 5.2 million years.

Previous observations of Abell 3558 found a cold front about 320,000 light-years northwest of the cluster’s center. In general, these so-called cold regions are the sharp surface brightness and discontinuity seen in X-ray images, where the decrease in surface brightness and gas pressure is accompanied by a jump in gas temperature, and the dense region is colder than rarefied. region.

The cold front detected in Abell 3558 is thought to be due to massive slippage, caused by the movement of a small cluster of galaxies, possibly SC 1327–312, or by an off-axis merger with a larger system. A team of astronomers led by Mohammad Mirakhor analyzed archival XMM-Newton images of Abell 3558 for more light from this cold front, resulting in the discovery of two new objects.

The researchers identified a double surface brightness discontinuity at large radii outside the center of Abell 3558 that had not been reported before. One of them is about 2 million light-years from the center of the cluster to the southeast and the other is located about 4 million light-years from the center of the cluster to the northwest.

Spectral analysis confirmed that these two discontinuities are indeed very cold boundaries. Based on the data collected, astronomers estimate that the cold zone in the southeast is about 8.5 billion years old.

The discovery made by the Mirakhor team makes Abell 3558 one of the few star clusters to host three or more cold boundaries. What’s more, the outer cold front is one of the coldest regions ever seen in the galaxy, located at a greater distance from the center than the coldest front observed in the galaxy.

According to the authors of this paper, their discovery suggests that the slip may extend beyond the cooling radius of the galaxy cluster, meaning it is a cluster-wide phenomenon.

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