In an article recently published on arXiv.org a team of astronomers presented a detection of an interesting object – so-called radio phoenix galaxy cluster. This object similarly to conventional radio galaxies emits a broad range of radio waves and is located in Abell 1033, a peculiar galaxy cluster which underwent a recent merger with another cluster of galaxies.
The modern science of astronomy suggests that there is a strong relation between galaxy cluster-scale radio emissions and cluster mergers. A possible explanation is that accretion shocks and large turbulent regions form during collisions and subsequently may generate intense emissions of radio waves. Such clusters with bright radio emissions are only detected in dynamic regions of the Universe, which further supports the influence of above-mentioned factors.
As the authors of the current study note, in Abell 1033 they observed a rare and less studied type of emission, the so-called radio phoenix. This type of emission was first described by Slee et al. in 2001. It is thought that a fossil radio plasma, or the plasma remaining from a previous episode of activity of active galactic nuclei (AGN) is compressed by a shock wave generated by a merger; this compression increases the strength of magnetic field inside the plasma and the energies of relativistic particles contained in the same region. The electrons from the fossil plasma are re-energized so they shine brightly again at radio wavelengths.
The detection of a rare event was made on June 6, 2014, using the Westerbork Synthesis Radio telescope (WSRT) which is considered to be the one of the most powerful radio telescopes in the world. Additional data was obtained from observations accomplished by Chandra observatory in February of 2013, and also from archival data from the Very Large Array and the Sloan Digital Sky survey.
After performing the galaxy number density and redshift analysis the researchers determined that Abell 1033 is composed of two subclusters. One of those subclusters also contains two tailed radio galaxies: the morphology of the ‘tails’ of these two galaxies allowed to confirm the merger scenario and to determine an approximate line of cluster motion (as shown in the image below).
The authors of the study say that further optical and multi-frequency radio observations of Abell 1033 are planned for the future and should give more detailed insights into the structure and origin of this peculiar and complex system.
Written by Alius Noreika