HOT TIMES FOR COOLING FLOWS

Mateusz Ruszkowski

Cooling flow cluster Non-cooling flow cluster

gas radiates X-rays & loses pressure support against gravity gas sinks towards the center to adjust to a new equilibrium

COOLING FLOW PROBLEMCOOLING FLOW PROBLEM

PROBLEMS • “COOLING FLOWS”

– No evidence for large mass dropout• Stars, absorbing gas

– Temperature “floor’’

Temp. drops by factor ~3

Sanders & Fabian 2002

CLUSTER HEATING appears to be:

• RELATIVELY GENTLE– No shock heating– Cluster gas convectively stable

– Abundance gradients not washed out

• DISTRIBUTED WIDELY – not too centrally concentrated– Entropy “floor” manifest on large scales– Needed to avoid cooling “catastrophe”

HEATING CANDIDATES

• AGN heating (Tabor & Binney, Churazov et al.)• Thermal conduction (Bertschinger & Meiksin,

Zakamska & Narayan, Fabian et at., Loeb)• Turbulent mixing (Kim & Narayan)

WE CALL THIS “EFFERVESCENT HEATING”

• Cluster gas heated by pockets of very buoyant (relativistic?) gas rising subsonically through ICM pressure gradient – Expanding bubbles do pdV work

• Dependent on two conditions:– Buoyant fluid does not mix (much) with cluster gas

persistent X-ray “holes”

– Acoustic & potential energy is converted to heat by damping and/or mixing

EFFERVESCENT HEATING: 1D MODEL

• “Bubbles” rise on ~ free-fall time • Assume

– Number flux of CR conserved – Energy flux decreases due to adiabatic losses

– Dissipation converts motion to heat ~locally

coolt

• Volume heating rate:

• Compare to cooling rate:

HEATING MODEL

rd

pd

r

p

r

ECRln

ln

4~

3

4/1

2

TTn 22 )(

TARGETS PRESSURE GRADIENT STABILIZES COOLING

Ruszkowski & Begelman 2002

1D ZEUS SIMULATIONS

Includes:

Conductivity @ Spitzer/4

Simple feedback in center

M

Ruszkowski & Begelman 2002

AGN, not conduction, dominates heating

ENTROPY PROBLEM IN THE ICM– entropy “floor”

– Supernova heating may be inadequate

3TLX

Roychowdhury, Ruszkowski, Nath & Begelman 2003Roychowdhury, Ruszkowski, Nath & Begelman 2003

Possible solutionsPossible solutions: Cooling --- gas cools and forms galaxies,

low entropy gas is removed; Voit et al. Turbulent mixing (Kim & Narayan) AGN heating --- gas is heated; entropy increases

relation ?

Edd1.0 LL

bulge4

BH 104 MM

Roychowdhury, Ruszkowski, Nath & Begelman 2003Roychowdhury, Ruszkowski, Nath & Begelman 2003

cluster3

bulge 102 MM

1

sun

cluster4510

serg

M

ML

clusterBH MM

Testing assumptions of the model

‘‘Pure’’ theory requiresLateral spreading of the buoyant gas must be significantSpreading must occur on the timescale comparable to or shorter than the cooling timescale

BUTBUT

Heating must be consistent with observationsNo convectionPreserved abundance gradientsCool rims around rising bubblesRadio emission less extended spatially than X-rays Sound waves

THE TOOL – the FLASH code• Crucial to model mixing and weak

shocks accurately– PPM code with Adaptive Mesh Refinement, e.g., FLASH,

better than lower-order, diffusive code, e.g., ZEUS

Chandra image

3C 84 andPerseus ClusterFabian et al. 2000

Note multiple “fossil” bubbles, not aligned with current radio jets

RAPID ISOTROPIZATIONRAPID ISOTROPIZATION – buoyant gas spreads laterally on dynamical timescale until it covers steradians4

Ruszkowski, Kaiser & Ruszkowski, Kaiser & Begelman 2003Begelman 2003

Chandra image

3C 84 and Perseus ClusterFabian et al. 2000

Cold rims, not strong

shocks

COOL RIMSCOOL RIMS – entrainment of lower temperature gas

Ruszkowski, Kaiser & Begelman 2003Ruszkowski, Kaiser & Begelman 2003

THE DEEPEST VOICE FROM THE THE DEEPEST VOICE FROM THE OUTER SPACEOUTER SPACE

Fabian et al. 2003

Unsharp masked Chandra image

X-ray temperatures

131 kpc

MEDIA CRAZEMEDIA CRAZE

SOUND WAVESSOUND WAVES

Ruszkowski, Kaiser Ruszkowski, Kaiser & Begelman 2003& Begelman 2003

Chandra image +1.7 GHz radio

3C 338 andAbell 2199Johnstone et al.

2002

“fossil” bubbles

Ruszkowski, Kaiser & Begelman 2003Ruszkowski, Kaiser & Begelman 2003

Conditions emulate Abell 2199, with cooling;

127 186 244 303 Myr

sergLAGN /1044

Radio: Higher contrasts, detectable only close to jet axis

X-rays: spread out laterally

“Ghost cavities” do not trace previous jet axis

3C 338 + Abell 2199(Johnstone et al. 2002)

CONCLUSIONSCONCLUSIONS

• No need for large mass deposition rates• Minimum temperatures around 1 keV• Entropy floor

• Significant and fast lateral spreading • Sound waves• Cool rims• Mismatch between X-ray and radio emission

SEMI-ANALYTICAL MODELSSEMI-ANALYTICAL MODELS

NUMERICAL SIMULATIONSNUMERICAL SIMULATIONS