Study sheds more light on the diffuse radio emission from galaxy cluster Abell 1213

European astronomers have observed a galaxy cluster called Abell 1213 using various spacecraft and ground-based facilities. The observations revealed essential information about the diffuse radio emission from this source. The results are published in a paper published on March 4th arXiv preprint server.

Galaxy clusters contain up to thousands of galaxies that are gravitationally bound together. They are the largest known gravitationally bound structures in the Universe and could serve as excellent laboratories for the study of galaxy evolution and cosmology.

At redshift 0.047, Abell 1213 is a impoverished, low-mass galaxy cluster dominated in its central region by radio galaxy 4C29.41 and two other radio galaxies. Previous observations of this cluster have revealed that it hosts a radio source believed to be a small radiohalo – a diffuse synchrotron source with low surface brightness.

A team of astronomers led by Walter Boschin of La Laguna University, Spain, has analyzed a huge data set from space telescopes and ground-based observatories to shed more light on the properties of Abell 1213, the nature of its radio source and its diffuser Emission.

“We used optical SDSS data to study the internal dynamics of the cluster. We also analyzed archived XMM-Newton X-ray data to reveal properties of its hot intracluster medium. Finally, we used recent LOFAR data at 144 MHz together with VLA data at 1.4 GHz to study the spectral behavior of the diffuse radio source,” the researchers write in the publication.

First, the observations showed that Abell 1213 has perturbed dynamics, as its brightest cluster galaxy (BCG) has a very significant intrinsic velocity. The results indicate that Abell 1213 consists of several galaxy groups and its core is quite complicated. In addition, blue, star-forming galaxies were found not to be confined to the peripheral regions of Abell 1213, which seems to indicate that the cluster formed through accretion of several poor groups rich in late-type galaxies.

Radio observations of Abell 1213 show that the diffuse radio emission is about 1.66 million light-years in size. However, it turned out that this radio emission does not follow the X-ray emission. Therefore, the extended source may not be a radio halo, but a tail of the central radio galaxy 4C29.41 that has been bent by interacting with the intracluster medium (ICM). In addition, the data provided some evidence of fragmented diffuse radio emissions at the cluster center, the nature of which is uncertain.

The astronomers also suspect that the source of the radio emission in Abell 1213 could be a radio relic, so ‘fossil’ electrons from 4C29.41 are accelerated again by a merger shock. They argue that the spectral index distribution supports this hypothesis.

“The radio source spectral index map is compatible with a relict interpretation, possibly due to merging in the NS or NE-SW direction, consistent with the substructures detected by the optical analysis. The fragmented, diffuse radio emissions at the cluster could be the surface brightness spikes of a faint central radio halo,” the researchers explained.

The paper’s authors noted that deeper X-ray observations of Abell 1213 are needed to draw definitive conclusions about the nature of its diffuse radio emission.

© 2023 Science X Network