Speaker
Description
Hydra A is a FR-I type radio galaxy located at the centre of the Abell 780 cluster with a redshift of z = 0.054. Previous observations of the radio galaxy have been conducted at low frequencies by the Very Large Array (VLA) telescope and using the L-band frequencies of the MeerKAT array telescope. The Chandra X-ray observatory also carried out a detailed survey of the X-ray emission from the radio galaxy. These observations gave us invaluable information regarding the morphology of the galaxy. They revealed that Hydra A is composed of: a bright central core, pair of relativistic jets, pair of inner radio lobes, pair of diffuse outer radio lobes with the south-facing lobe having a tail-like extension and three pairs of X-ray cavities surrounding the lobes.
A spectral break in the radio spectrum is exhibited by the low frequency observations of Hydra A and this has been ascribed to the process of spectral ageing. The spectral age is the time it takes an electron in the lobe region of a radio galaxy to radiate all of its energy through synchrotron and inverse-Compton emission. Minimal research has been done on the tail-like region of Hydra A. One of the few studies done used MeerKAT’s L-band frequencies and reported the tail-like region as having a spectral index that is dissimilar to the lobe regions. This raised questions about the spectral age, electron injection history and possible emission mechanisms in the tail-like region.
The main aim of our research study was to directly measure the spectral break frequency in the radio spectrum of the tail-like region of Hydra A using MeerKAT's UHF observations. This meant we could directly determine the spectral age of the region and see whether it corroborates the previous L-band study and comment on the history of electron injection in the region. In addition to the tail-like region, the southern outer lobe and northern lobe regions were also investigated with the data reduction process producing four UHF-band observations images of Hydra A at central frequencies of 612 MHz, 748 MHz, 884 MHz and 1020 MHz. The Kardashev-Pacholcyzk (KP) spectral age model was best suited to describe the spectrum and we used it to determine the spectral ages of the three regions. The main conclusion was the supplementary UHF dataset being consistent with previous observations without significantly improving the constraints on the spectral age. The spectral age of the tail region was 140.24 Myrs, making it the oldest region of the galaxy which can be attributed to reduced contact with the relativistic jets which continuously inject new electron populations.