High frequency radio imaging of 3CR 403.1 with the Sardinia Radio Telescope

TL;DR

This study uses high-frequency radio imaging from the Sardinia Radio Telescope to analyze the spectral, polarimetric, and environmental properties of the radio galaxy 3CR 403.1, revealing insights into its magnetic field, age, and intracluster medium.

Contribution

First high-frequency radio observations of 3CR 403.1 combined with archival data to study its spectral, magnetic, and environmental characteristics.

Findings

Magnetic field in lobes estimated at 2.4 μG.

Source age approximately 100 million years.

Detected asymmetry in Faraday rotation and magnetic field constraints in the ICM.

Abstract

We present multifrequency observations of the radio source 3CR 403.1, a nearby (z=0.055), extended ($\sim$0.5 Mpc) radio galaxy hosted in a small galaxy group. Using new high frequency radio observations from the Sardinia Radio Telescope (SRT), augmented with archival low frequency radio observations, we investigated radio spectral and polarimetric properties of 3CR 403.1. From the MHz-to-GHz spectral analysis, we computed the equipartition magnetic field in the lobes to be B$_{eq}$=2.4~$\mu$G and the age of the source to be $\sim$100 Myr. From the spectral analysis of the diffuse X-ray emission we measured the temperature and density of the intracluster medium (ICM). From the SRT observations, we discovered two regions where the radio flux density is below the background value. We computed the Comptonization parameter both from the radio and from the X-ray observations to test if the Sunyaev-Zel'dovich effect is occurring here and found a significant tension between the two estimates. If the negative signal is considered as real, then we speculate that the discrepancy between the two values could be partially caused by the presence of a non-thermal bath of mildly relativistic ghost electrons. From the polarimetric radio images, we find a net asymmetry of the Faraday rotation between the two prominent extended structures of 3CR 403.1, and constrain the magnetic field strength in the ICM to be 1.8-3.5 $\mu$G. The position of 3CR 403.1 in the magnetic field-gas density plane is consistent with the trend reported in the literature between central magnetic field and central gas density.