Speaker
Description
In the last two decades, an increasing number of studies of galaxy clusters and groups have demonstrated the importance of the interplay between the Intra-Cluster Medium (ICM) and Active Galactic Nuclei (AGN) for the overall evolution of the largest-scale structures. However, only in recent years, thanks to new-generation instruments such as LOFAR, we were able to move these investigations to the lowest radio frequencies. This is essential since, because of the shape of the synchrotron spectrum, we are potentially able to assess the effects of past AGN outbursts on the host environment and how it affected its evolution.
In this talk, I will present new observations of Abell 1213, a galaxy group that recently fell under the spotlight for the presence of a long tail of diffuse emission in the radio band whose origin is hard to explain. Our study includes LOFAR and uGMRT proprietary data at 54 and 380 MHz, as well as LOFAR VLBI images from LoTSS at 144 MHz. The long tail extends for ~500 kpc Eastwards from the AGN and shows multiple sub-components. While a recent study gave a tentative classification as a radio relic, we show spectral index maps that hint a different origin, most likely linked to old AGN plasma ejected during past outbursts. The analysis of the thermal emission from the Intra-Group Medium (IGrM) support this hypothesis, as it hints to a physical connection with the non-thermal component. By sampling the spectral index along the extended tail and the AGN, we show that within the first 150 kpc the source shows an inverted spectrum. Finally, from LOFAR images there are hints of a faint, diffuse component with an extremely steep spectrum (𝛼<-3) which surrounds the central AGN, and whose nature is still unclear.
