A study of the lobes of radio galaxy Hydra A using MeerKAT observations

Abstract

Hydra A is a powerful radio galaxy located at the center of the galaxy cluster Abell 780. It hosts a pair of hundred-kiloparsec scale radio lobes that are being powered by the closest of the three most powerful cluster-scale AGN outbursts known to date. In this study we use observations of Hydra A carried out using the MeerKAT radio telescope in the L-band. We reduced the data using the CARACal pipeline and present four radio maps at 1000 MHz, 1100 MHz, 1330 MHz and 1485 MHz. We find the radio morphology of Hydra A can be described by a core region, a pair of bright inner lobes, a pair of large diffuse outer lobes- one in the northern di- rection and one in the southern direction- and an interesting tail-like region that extends out from the southern outer lobe. In this study, we analyse the northern outer lobe, southern outer lobe and tail-like region in detail. This includes comput-ing the radiative flux densities of each region and performing a spectral analysis of each region. We find that the population of synchrotron-emitting electrons in the tail-like region has undergone significant spectral aging and is most likely the old-est region in the Hydra A system. We model the spectrum of Hydra A and find the Kardashev-Pacholczyk model for spectral aging satisfactorily represents the spec-trum. We set constraints on the age and magnetic field values for all three regions. It is most likely the case that the northern and southern lobes are still connected to the jets and are being injected with young electrons, whereas, the tail-like region is completely disconnected from the jets and is a remnant of an older generation of AGN activity. We estimate the age of the Hydra A system to be ∼ 140 Myrs, which is consistent with previous age estimates.