Properties of a galaxy in deep multiwavelength surveys

Abstract

The evolution of distant galaxies with redshift 0 < z < 2 can be observationally determined by separately tracing the evolution of stars, gas and dust in these galaxies. To do this effectively, one needs to use far-infrared data to trace the dust; ultraviolet, optical and radio data to trace star formation and H-alpha and HI radio observations to trace the ionised and neutral gas, respectively. In addition, we can combine optical spectroscopy with X-ray and radio imaging to understand the properties of the supermassive black holes at the centres of galaxies that manifest as Active Galactic Nuclei. In this project, we used archival observations at many wavelengths from a number of space and ground based facilities such as XMM/Newton, Spitzer, Subaru, VLA and GMRT.

We investigated the nature of extended, diffuse, radio and X-ray emission associated with the lobes of a giant radio galaxy J021659-044920 at redshift z = 1.325. X-ray emission is nearly co-spatial with the radio lobes and 0.3 – 10 keV spectrum can be best fitted with a power law of photon index 1.86, consistent with its plausible origin as Inverse Compton scattering of the Cosmic Microwave Background (ICCMB) photons. We estimate the magnetic field in radio lobes using both X-ray and radio observations. Using both X-ray and radio observations we estimate the magnetic field in the lobes to be 3.3 μG. The magnetic field estimate based on energy equipartition is ~ 3.5 μG. Assuming ICCMB, we estimated minimum energy in the particles in the lobes to be 4.2 × 10 59 erg. Notably, radio and X-ray emission from the central AGN remains undetected in present observations inferring that the AGN activity has recently stopped. Our work present a case study of a rare example of a giant radio galaxy caught in dying phase in the distant universe.