The Moderate Cooling Flow Model and Feedback in Galaxy Formation

TL;DR

This paper investigates feedback heating in galaxy clusters, emphasizing the role of cold blobs and specific jet models in inflating bubbles and heating the intracluster medium, challenging some existing models.

Contribution

It introduces a new model of SMBH accretion via cold blobs and demonstrates the effectiveness of slow, wide, or precessing jets in bubble formation and ICM heating.

Findings

Cold dense blobs drive SMBH accretion, replacing Bondi accretion.

Slow, wide, or precessing jets inflate stable bubbles.

Bubble inflation excites sound waves and shocks for heating.

Abstract

For the recent four years we have been studying feedback heating in cooling flow (CF) clusters by AGN activity that inflate bubbles by jets; this short contribution to a meeting summarizes our main results. To achieve our results we had to self-consistently inflate the bubbles with jets, rather than inject them artificially. Our main results are as follows (1) Feedback mechanisms that are based on Bondi accretion fail. Instead, the accretion to the central super-massive black hole (SMBH) is in the form of cold dense blobs that fall-in from an extended region. (2) Slow massive wide (SMW) jets, or rapidly precessing jets, can inflate bubbles similar to those observed in CF clusters. (3) Contrary to some claims in the literature, the inflated bubbles are stable for a relatively long time, becoming unstable only at later times. (4) A single bubble inflation episode excites multiple sound waves and shocks. These can then heat the intracluster medium (ICM). (5) Mixing of the bubble material to the ICM is efficient, and can serve as a main heating channel. (6) The heating processes work in all directions, and can explain the heating of the ICM in CF in clusters and in galaxies.