Radio mode feedback: Does relativity matter?

TL;DR

This paper compares relativistic and classical models of radio jet feedback in active galaxies, showing that relativistic jets are more efficient at heating the ambient medium and influence galaxy evolution more significantly.

Contribution

It demonstrates that classical models underestimate cavity pressure and heating efficiency, highlighting the importance of relativistic effects in jet feedback simulations.

Findings

Relativistic jets increase cavity pressure by at least a factor of 2.

Relativistic jets heat the ambient medium about 20% more efficiently.

The heated volume by relativistic jets is 2 to 10 times larger over time.

Abstract

Radio mode feedback, associated with the propagation of powerful outflows in active galaxies, is a crucial ingredient in galaxy evolution. Extragalactic jets are well collimated and relativistic, both in terms of thermodynamics and kinematics. They generate strong shocks in the ambient medium, associated with observed hotspots, and carve cavities that are filled with the shocked jet flow. In this Letter, we compare the pressure evolution in the hotspot and the cavity generated by relativistic and classical jets. Our results show that the classical approach underestimates the cavity pressure by a factor larger or equal to 2 for a given shocked volume during the whole active phase. The tension between both approaches can only be alleviated by unrealistic jet flow densities or gigantic jet areas in the classical case. As a consequence, the efficiency of a relativistic jet heating the ambient is typically around 20% larger compared with a classical jet, and the heated volume is 2 to 10 times larger during the time evolution. This conflict translates into two substantially disparate manners, both spatially and temporal, of heating the ambient medium. These differences are expected to have relevant implications on the star formation rates of the host galaxies and their evolution.