Formation of mega-parsec giant radio sources from hosts residing in dark matter halos with normal hot baryonic gas fractions

Abstract

Mega-parsec giant radio sources (GRSs) have been known for decades. Their known population has soared from several hundred to more than $10^4$ in recent years. However, the formation mechanisms of GRSs remain elusive. In this work, we study the formation and properties of GRSs associated with dark matter halos of different masses and normal gas density environment. We use magnetohydrodynamic simulations to study the formation of GRSs from hosts residing in dark matter halos with masses of $10^{13}$, $10^{14}$ and $10^{15}$ solar masses, adopting normal hot baryonic gas fractions in ranges (0.02-0.1, 0.05-0.1, and 0.1-0.15) and varying density profiles. We inject jet energy of 0.06 percent of the central black hole's relativistic energy in their host galaxies with power of 0.05 percent of the Eddington luminosity in most runs. The successful formation of GRSs from hosts in dark matter halos with normal hot baryonic gas fractions indicates that an unusual low-density gas environment is not a prerequisite for their formation. The propagation of radio lobes can be slower in halos with sufficiently low or high central density and pressure, as a much lower central pressure cannot sufficiently collimate the jet and produces wider, less penetrating lobes, whereas an atmosphere with sufficiently high pressure enhances the interaction between the jet and the surrounding medium. Assuming equipartition between non-thermal electron and magnetic energy, the evolution of the simulated GRSs in the radio power--linear size diagram shows that the radio power of most simulated sources within halo masses of $\rm 10^{13}$ and $\rm 10^{14} M_\odot$ can reach values comparable to observational data at similar physical scales. The simulated sources with a shorter jet duration than other sources become faint remnant sources when they propagate to GRS scales.