Astronomers observe a strong shock front in galaxy cluster SPT-CLJ 2031-4037

Astronomers from the University of Alabama in Huntsville, using NASA's Chandra X-ray spacecraft, have made an intriguing discovery in the merging galaxy cluster named SPT-CLJ 2031-4037. In a recently published research paper on the pre-print server arXiv, they reported the observation of a strong shock front within this particular galaxy cluster, a phenomenon not commonly observed.

Galaxy clusters are formed through the merging of smaller subclusters and consist of thousands of galaxies held together by gravity. These clusters are incredibly large, making them perfect subjects for the study of galaxy evolution and cosmology.

Mergers between galaxy clusters are some of the most energetic events in the universe, second only to the Big Bang. During these mergers, a fraction of the kinetic energy is dissipated into the intracluster medium, resulting in shocks and turbulence. These shock fronts manifest as sharp discontinuities in X-ray brightness and temperature, providing astronomers with a unique opportunity to study and comprehend these complex merger systems and their geometry.

SPT-CLJ 2031-4037, also known as SPT J2031, is a merging galaxy cluster with a redshift of 0.34. It is an extremely massive system with an estimated mass of approximately 800 trillion solar masses and exhibits an X-ray luminosity of 1.04 quattuordecillion erg/s.

Under the leadership of Purva Diwanji from the University of Alabama, a team of astronomers conducted an extensive search for shock fronts within SPT J2031, utilizing the Chandra X-ray observatory. The researchers employed the Chandra Advanced CCD Imaging Spectrometer (ACIS) detector in the Very Faint (VFAINT) mode, with a total observation time of 256 ks divided into 10 separate observations.

Their observations led to the detection of two shock fronts within SPT J2031. One shock front, stronger in intensity, was observed in the northwest direction, while a weaker shock front was found in the southeast (the southeastern edge). The stronger shock front demonstrated a density jump of 3.16 across the sharp surface brightness edge along with a Mach number of 3.36. Conversely, the weaker shock front showcased a density jump of 1.53 and a Mach number of 1.36.

Notably, these findings make SPT J2031 one of the few merging systems with a high Mach number surpassing 2.0. Only a limited number of merger shock fronts with such values have been discovered by Chandra.

Additionally, the study unveiled that SPT J2031 exhibits merger geometry. It was also observed that the post-shock electron temperature of the stronger shock front is lower than the temperature predicted by the instant shock heating model, thereby favoring the collisional equilibration model. These conclusions are coherent with previous research findings pertaining to SPT J2031.

In conclusion, the discovery of a strong shock front in SPT-CLJ 2031-4037 provides astronomers with invaluable insights into the complex processes involved in merging galaxy clusters. Through meticulous observation and research, scientists continue their quest to unlock the mysteries of the universe.