Non-thermal emissions from a head-tail radio galaxy in 3D magnetohydrodynamic simulations

TL;DR

This study uses 3D magnetohydrodynamic simulations to investigate non-thermal emissions from a head-tail galaxy, highlighting the importance of cosmic-ray reacceleration and predicting observable X-ray signals.

Contribution

The paper introduces detailed MHD simulations of jet-wind interactions in galaxy clusters, emphasizing cosmic-ray reacceleration's role in radio emissions and exploring the origin of collimated synchrotron threads.

Findings

Reacceleration is crucial for matching observed radio properties.

Hard X-ray emissions may be detectable by satellites like FORCE.

Elongated flux tubes can persist for over 300 Myr without disruption.

Abstract

We present magnetohydrodynamic simulations of a jet-wind interaction in a galaxy cluster and the radio to gamma-ray and the neutrino emissions from this "head-tail galaxy". Our simulation follows the evolution of cosmic-ray (CR) particle spectra with energy losses and the stochastic turbulence acceleration. We find that the reacceleration is essential to explain the observed radio properties of head-tail galaxies, in which the radio flux and spectral index do not drastically change. Our models suggest that hard X-ray emissions can be detected around the head-tail galaxy in the Perseus cluster by the hard X-ray satellites, such as FORCE, and it will potentially constrain the acceleration efficiency. We also explore the origin of the collimated synchrotron threads, which are found in some head-tail galaxies by recent high-quality radio observations. Thin and elongated flux tubes, connecting the two tails, are formed by strong backflows at an early phase. We find that these threads advect with the wind for over 300 Myr without disrupting. The radio flux from the flux tubes is much lower than the typical observed flux. An efficient CR diffusion process along the flux tubes, however, may solve this discrepancy.