European astronomers have observed the cluster of galaxies, known as Abell 1213, using various spacecraft and ground facilities. The observations made it possible to obtain important information about the diffuse radio emission of this source. The results are reported in an article published March 4, 2023 on the preprint server arXiv.
Clusters of galaxies contain up to a thousand galaxies bound by gravity. They are the largest known gravitationally bound structures in the universe and can serve as excellent laboratories for studying galaxy evolution and cosmology.
At a redshift of 0.047, Abell 1213 is a poor, low-mass cluster of galaxies dominated by the radio galaxy 4C29.41 and two other radio galaxies in its central region. Previous observations of this cluster have shown that it contains a radio source that is believed to be a small radio halo, a low-brightness diffuse synchrotron source.
A team of astronomers led by Walter Boskin of the University of La Laguna, Spain, analyzed a huge dataset from space telescopes and ground-based observatories to shed more light on the properties of Abell 1213.
First, observations have shown that Abell 1213 exhibits disrupted dynamics, as the brightest galaxy in the cluster has a very significant peculiar velocity. The results show that the Abell 1213 cluster consists of several groups of galaxies, and its core is quite complex. In addition, blue star-forming galaxies have been found not to be limited to the peripheral regions of Abell 1213, and this seems to indicate that the cluster formed from the accretion of several groups rich in late-type galaxies.
Radio observations from Abell 1213 show that the diffuse radio emission is about 1.66 million light-years across. However, it turned out that this radio emission does not follow the X-ray emission. Consequently, the extended source may not be a radio halo, but the tail of the central radio galaxy 4C29.41, a curved interaction with the intracluster medium. In addition, the data provided some evidence of fragmentary diffuse radio emission at the center of the cluster, the nature of which is unclear.
Astronomers also speculate that a radio relic may be the source of the radio emission in Abell 1213, hence 4C29.41’s “fossil” electrons are being re-accelerated by the impact due to the merger. They argue that the distribution of the spectral index supports this hypothesis.
The authors of the paper noted that deeper X-ray observations of Abell 1213 are needed to draw definitive conclusions about the nature of its diffuse radio emission.
Source: W. Boschin et al, Optical/X-ray/radio view of Abell 1213: A galaxy cluster with anomalous diffuse radio emission, arXiv (2023). 184.108.40.206/abs/2303.02528