Active galactic nucleus jet feedback in hydrostatic halos

TL;DR

This study uses simulations to analyze how different types of AGN jets influence cooling flows in galaxy clusters, highlighting the importance of jet properties and their effects on halo gas over 50 million years.

Contribution

It demonstrates that light, thermal AGN jets can effectively delay cooling flows without requiring precession or wide angles, and compares jet feedback to kinetic wind models.

Findings

Light, thermal jets delay cooling flows more effectively than heavy, kinetic jets.

Jet properties within models are the main source of uncertainty in feedback predictions.

Jets influence hot halo gas more, while winds impact star-forming regions more locally.

Abstract

Feedback driven by jets from active galactic nuclei is believed to be responsible for reducing cooling flows in cool-core galaxy clusters. We use simulations to model feedback from hydrodynamic jets in isolated halos. While the jet propagation converges only after the diameter of the jet is well resolved, reliable predictions about the effects these jets have on the cooling time distribution function only require resolutions sufficient to keep the jet-inflated cavities stable. Comparing different model variations, as well as an independent jet model using a different hydrodynamics code, we show that the dominant uncertainties are the choices of jet properties within a given model. Independent of implementation, we find that light, thermal jets with low momentum flux tend to delay the onset of a cooling flow more efficiently on a $50$ Myr timescale than heavy, kinetic jets. The delay of the cooling flow originates from a displacement and boost in entropy of the central gas. If the jet kinetic luminosity depends on accretion rate, collimated, light, hydrodynamic jets are able to reduce cooling flows in halos, without a need for jet precession or wide opening angles. Comparing the jet feedback with a `kinetic wind' implementation shows that equal amounts of star formation rate reduction can be achieved by different interactions with the halo gas: the jet has a larger effect on the hot halo gas while leaving the denser, star forming phase in place, while the wind acts more locally on the star forming phase, which manifests itself in different time-variability properties.