hot times for cooling flows
DESCRIPTION
HOT TIMES FOR COOLING FLOWS. Mateusz Ruszkowski. Cooling flow cluster Non-cooling flow cluster. COOLING FLOW PROBLEM. gas radiates X-rays & loses pressure support against gravity gas sinks towards the center to adjust to a new equilibrium. PROBLEMS. “COOLING FLOWS” - PowerPoint PPT PresentationTRANSCRIPT
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HOT TIMES FOR COOLING FLOWS
Mateusz Ruszkowski
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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
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PROBLEMS • “COOLING FLOWS”
– No evidence for large mass dropout• Stars, absorbing gas
– Temperature “floor’’
Temp. drops by factor ~3
Sanders & Fabian 2002
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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”
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HEATING CANDIDATES
• AGN heating (Tabor & Binney, Churazov et al.)• Thermal conduction (Bertschinger & Meiksin,
Zakamska & Narayan, Fabian et at., Loeb)• Turbulent mixing (Kim & Narayan)
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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
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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
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• 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
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Ruszkowski & Begelman 2002
1D ZEUS SIMULATIONS
Includes:
Conductivity @ Spitzer/4
Simple feedback in center
M
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Ruszkowski & Begelman 2002
AGN, not conduction, dominates heating
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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
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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
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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
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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
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Chandra image
3C 84 andPerseus ClusterFabian et al. 2000
Note multiple “fossil” bubbles, not aligned with current radio jets
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RAPID ISOTROPIZATIONRAPID ISOTROPIZATION – buoyant gas spreads laterally on dynamical timescale until it covers steradians4
Ruszkowski, Kaiser & Ruszkowski, Kaiser & Begelman 2003Begelman 2003
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Chandra image
3C 84 and Perseus ClusterFabian et al. 2000
Cold rims, not strong
shocks
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COOL RIMSCOOL RIMS – entrainment of lower temperature gas
Ruszkowski, Kaiser & Begelman 2003Ruszkowski, Kaiser & Begelman 2003
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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
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MEDIA CRAZEMEDIA CRAZE
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SOUND WAVESSOUND WAVES
Ruszkowski, Kaiser Ruszkowski, Kaiser & Begelman 2003& Begelman 2003
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Chandra image +1.7 GHz radio
3C 338 andAbell 2199Johnstone et al.
2002
“fossil” bubbles
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Ruszkowski, Kaiser & Begelman 2003Ruszkowski, Kaiser & Begelman 2003
Conditions emulate Abell 2199, with cooling;
127 186 244 303 Myr
sergLAGN /1044
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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)
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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