|Description:|| Radio halos are giant diffuse synchrotron emission found at the center of some merging galaxy clusters. In the past, they were described as smooth and regular sources with a morphology recalling that of the X-ray emitting gas. Highly sensitive observations performed with LOFAR-HBA are changing our view of radio halos, unveiling the presence of a large diversity of surface brightness structures embedded in the diffuse emission.|
This image shows the complex radio emission from the nearby galaxy cluster Abell 2255 as observed by LOFAR in the context of the LOFAR Two-Meter Sky Survey (LoTSS, Shimwell et al. 2017). Abell 2255 is a spectacular system that in its central ~10 Mpc^2 region shows a plethora of emission on different scales, from tens of kpc to above Mpc sizes. Among the numerous interesting features observed, we note the presence of filaments in the halo, emission from radio galaxies with extended tails, and emission from bright revived fossil plasma. The sources labelled in black were known from previous observations, while those labelled in blue and have been discovered only thanks to the high resolution and high sensitivity of LOFAR to low frequency radiation.
Reaching noise levels below 100 muJy/beam, this LOFAR image is among the deepest and most detailed cluster image at low frequency ever obtained so far. Being one of the most intricate diffuse radio sources known to date, Abell 2255 has been chosen to be the first LOFAR galaxy cluster deep field.
The results based on the analysis of LoTSS observations of this galaxy cluster have been recently presented and discussed in the article "The beautiful mess in Abell 2255", by Botteon et al. (2020), accepted for publication in The Astrophysical Journal (arXiv:2006.04808).
|Copyright:||Copyright © 2020 Andrea Botteon, accepted for publication in ApJ, https://arxiv.org/abs/2006.04808|