Astronomers gain insights into galaxy cluster G113 undergoing merger

European astronomers recently delved into the mysteries of the galaxy cluster known as PSZ2G113.91-37.01, or G113 for short, utilizing ESA’s XMM-Newton satellite and the Low-Frequency Array (LOFAR). Their findings, published on the arXiv pre-print server on October 5, shed new light on the properties and nature of this enigmatic cluster.

Galaxy clusters, massive conglomerations of thousands of galaxies bound by gravity, offer invaluable insights into galaxy evolution and cosmology. These colossal structures form through the accumulation of mass and infall of smaller sub-structures, making them ideal laboratories for scientific exploration.

G113, discovered in 1999, is a galaxy cluster with a redshift of 0.371. It possesses a staggering mass of about 758 trillion times that of our Sun, spanning approximately 4 million light-years in radius. Notably, G113 harbors a radio halo and two radio relics, making it a compelling subject for study. Surprisingly, it had eluded detailed observation by major X-ray satellites until now.

A team of astronomers, led by Maria Giulia Campitiello from the University of Bologna in Italy, decided to rectify this knowledge gap. They embarked on an X-ray investigation of G113 as part of the Cluster HEritage project with XMM-Newton, dubbed CHEX-MATE. Their study was bolstered by data from the LOFAR Two-meter Sky Survey-Data release 2 (LoTSS-DR2).

The findings unveiled that G113 is currently experiencing a merger along its north-south axis, affirming the presence of a radio halo in the central region and two radio relics. Strikingly, these relics are oriented perpendicular to the merger axis, with one located in the northern region and the other in the southern region.

Analyzing the X-ray data, the astronomers identified a distinct change in surface brightness in the northern part of G113, which they categorized as a “cold front.” Additionally, a temperature map exposed another cold area in the southern portion of the cluster.

The study divulged that the spectral index in the halo region averages around -1.15, with a standard deviation of 0.23. Notably, the results hint at a shift in the spectral profile in the northern front of the northern relic, potentially due to particles accelerated by an outward-moving shockwave.

Moreover, the researchers conducted a meticulous analysis of X-ray and radio emissions in both the halo and northern relic regions of G113, revealing a strong correlation within the halo and an intriguing anti-correlation within the relic. This discovery aligns with previous research.

In summary, the authors of this study propose further observations to unravel the intricate physical processes underlying these observed correlations and anti-correlations.

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