# Presentation: 164619

## Heating in cluster cool cores

-  **Mateusz Ruszkowski**
**University of Michigan**

## People (on the papers discussed in this talk):

- Peng Oh
- Fulai Guo
- Alexis Finoguenov
- Christine Jones
- Alexey Vikhlinin
- E. Mandell
- Ian Parrish
- Torsten Ensslin
- Marcus Bruggen
- Mitch Begelman
- Christoph Pfrommer
- Sebastian Heinz
- Eugene Churazov

## Outline

- Global stability of heated cool cores
- Reality check: observations of M84 an excuse to study:
- bubbles, waves, CR and their escape
- Stability of magnetized bubbles
- Escape of non-thermal particles from bubbles into the ICM
- Escape of CR from cool cores and convective stability

##    cool core cluster        non-cool core cluster

-    cool core cluster        non-cool core cluster

- 50-70% of clusters have cool cores

## Semi-analytical approach:

-         resolution !!
-  easy to search the parameter space
-  better physical insight

**Notes:**
1st order model

## Strongly destabilizing

- Strongly destabilizing

- x

- T

- heat flow

- stabilizing

- stabilizing

- spatial heating profile less important than
- the feedback itself

## Background model fits the data

##   We want to study the whole range cluster parameters, so ...

-   We want to study the _whole range cluster parameters_, so ...
-   take background profiles
-   apply Lagrangian perturbations and linearize the hydro equations
-   study all growing (unstable) and decaying (stable) solutions

## low accretion rates

-  efficiency threshold for stability
-  efficiencies agree with
-     Allen et al. 2006
-     Merloni & Heinz 2007
-     Churazov et al. 2001

**Guo, Oh & Ruszkowski 2008**

## Bimodality ! 

- _Bimodality !_
- cool core
- non cool core

- unstable

- stable

- stable

- stabilized by AGN + conduction
- stabilized by conduction

**Guo, Oh & Ruszkowski 2008**

- Two diagrams

## hint for bimodality

**Ruszkowski & Begelman 2002**

## Trends seen in the data

- _Trends seen in the data_

**Dunn & Fabian 2008**

- AGN on
- low central T
- low central entropy
- short central cooling time

- AGN off
- high central T
- High central entropy
- Long central cooling time

## Rafferty et al. 2008

**Rafferty et al. 2008**

- Short central cooling time            Young AGN bubbles
- Low central entropy            Star formation & AGN feeding

- See also Mark Voit’s talk on the effects of conduction on AGN feeding

## The model is broadly consistent with the data

- Shown for the first time that AGN + conduction can heat the cool cores across a range of cluster parameters in a **stable** fashion
- The model naturally explains why clusters come in **cool core **and** non-cool**** ****core** varieties

## Reality check - AGN feedback in M84 as an excellent lab

-   Bubbles
-   Waves
-   Escape of cosmic rays from the bubbles
-   ISM “weather”

**Finoguenov, Ruszkowski, Jones, Bruggen, Vikhlinin, Mandell 2008**

**Notes:**
Step back

## Deep ~ 100 000 second Chandra observation of M84

- Deep ~ **100 000** second *Chandra *observation of M84

- Russian doll X-ray cavities
- relative motion of the AGN
- with respect to the ISM
- (distorted cavities)

- direction of M84 motion
- (speed comparable to cavity
- expansion velocity)

##  Orange - nonthermal 

-  **Orange** - nonthermal
-                    (radio) mission

**Green** - large scale
-              X-ray emission

**Blue** - small scale
-                X-ray emission

**Non-thermal particles** (cosmic rays)
- escape and “pollute” the ISM

- cross-field cosmic ray escape ?

## pressure

- entropy

**Finoguenov, Ruszkowski, Jones, Bruggen, Vikhlinin, Mandell 2008**

- Ratio of the observed pressure and entropy to their mean profiles
- First application of Voronoi tessellation method to *Chandra* data

- low entropy,
- entrainment

- overpressured
- walls/waves
- mildly
- supersonic
- expanssion

## Synthetic “M84” replica !! 

***FLASH*** code AMR simulation of
- AGN feedback
- Bruggen, Ruszkowski, Hallman 2005

- waves detach
- from the bubble
- and dissipate via
- transport processes

- “Russian doll”
-  bubble

- bubble distorted by the
- relative AGN-ISM motion

- Before
- After

**Synthetic “M84” replica !!**

## M84 energetics

**M84 energetics**

- - wave-to-bubble ratio decreases with the distance
- - significant energy in the waves

## Magnetic fields in the ICM

**Magnetic fields in the ICM**

- rotation measure map

- Power spectrum of B-field fluctuations
- (Ensslin & Vogt 2005)

**Maximum near bubble size !**
**          ****magnetic draping**

## 3D MHD simulations with the PENCIL code 

- 3D MHD simulations with the *PENCIL* code

**Ruszkowski, Ensslin, Bruggen, Heinz, Pfrommer 2007**

## Modes of escape of non-thermal particles from the bubbles

**Cross-field diffusion**
**(**recall M84)

**Interface B-flux tubes**
- (e.g., in the bubble wakes
-  or due to
- “piercing” by the jet - recall M84)

## Theoretical suggestion (Ensslin 2003) 

- Observationally-based suggestion (Mathews & Brighenti 2007)

## anisotropic particle escape 

- isotropic

- anisotropic

- Ruszkowski, Ensslin, Bruggen, Begelman, Churazov 2008

**3D MHD** simulations of
_**anisotropic particle**__ __**escape**_
- from the bubbles

## Escape of non-thermal particles from the AGN bubbles

- Ruszkowski, Ensslin, Bruggen, Begelman, Churazov 2008

- 50% of non-thermal
- Particles escape

**Escape** of non-thermal particles from the AGN bubbles

- Isotropic case
- most particles escape

## excitation

**excitation**

- X-rays from ICM ?
- Fabian et al. 2003
- Star clusters ?
- Hatch et al. 2006
- Conduction ?
- Donahue et al. 2000
- or
**Cosmic ray heating ?**
**Diffusion in the bubble wake**
- Ruszkowski et al. 2008
- Ferland et al. 2008 (w/ *CLOUDY*)

## Perrish & Stone 2005

**Perrish & Stone 2005**
**Chandran 2001**
**Ruszkowski & Parrish 2008, in prep.**

- buoyancy

- expansion

- anisotropic
- energy flow
- along B-field

- escape of CR from cluster centers
- via the instability driven by
**anisotropic **
**energy transport**

- classical MRI

- gravity

## PENCIL code results

- linear theory

***PENCIL***** code results**

**Ruszkowski & Parrish 2008**, in prep.

## gravity

- the instability develops on the dynamical timescale

## Gas overturn due to the convective instability ?

**Gas overturn due to the convective instability ?**

- Perseus (Sanders & Fabian 2007)

- Centaurus (Sanders & Fabian 2002)

- A2199 (Johnstone et al. 2002)

## Summary

**cool core - non cool core bimodality**
-            - explained in a semianalytical study of global stability of clusters
-            - cool core stabilized by AGN, non-cool core by conduction
-            - no fine-tuning is required
**M84 as an example of AGN feedback**
-           - significant energy in waves
-           - evidence for the escape of non-thermal particles from the AGN bubbles
**Simulations with B-fields**
-         - magnetic draping can efficiently prevent bubbles from disruption
-              even for very weak magnetic fields
**Simulations with anisotropic CR leakage**
-         - difficult to confine all CRs in bubbles
-           - CR can provide the excitation mechanism for the filaments
**Simulations of plasma instabilities**
-        - non-thermal particles can escape cluster centers on a dynamical timescale
-             turbulent heating, metallicity profiles

## Slide 33

## Slide 34

## Dunn & Fabian 2005

- Rafferty et al. 2006

## Slide 36

## Sanders & Fabian 2007

**Sanders & Fabian 2007**

## waves detach 

**waves detach **
**from the bubbles**

**“****Russian doll” **
** ****bubble**

**bubble distorted by the**
**relative AGN-ISM motion**

## waves detach 

**waves detach **
**from the bubbles**

**“****Russian doll” **
** ****bubble**