HOT TIMES FOR COOLING FLOWS Mateusz Ruszkowski Cooling

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” – No evidence for large mass dropout • Stars, absorbing gas – Temperature “floor’’ Sanders & Fabian 2002 Temp. drops by factor ~3

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)

• Cluster gas heated by pockets of very buoyant (relativistic? ) gas rising subsonically through ICM pressure gradient – Expanding bubbles do pd. V 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 WE CALL THIS “EFFERVESCENT HEATING”

EFFERVESCENT HEATING: 1 D 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

HEATING MODEL TARGETS PRESSURE GRADIENT STABILIZES COOLING • Volume heating rate: • Compare to cooling rate:

1 D ZEUS SIMULATIONS Ruszkowski & Begelman 2002 Includes: Conductivity @ Spitzer/4 Simple feedback in center

Ruszkowski & Begelman 2002 AGN, not conduction, dominates heating

ENTROPY PROBLEM IN THE ICM entropy “floor” – Supernova heating may be inadequate – Possible solutions: 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 Roychowdhury, Ruszkowski, Nath & Begelman 2003

relation ? Roychowdhury, Ruszkowski, Nath & Begelman 2003

Testing assumptions of the model ‘‘Pure’’ theory requires Lateral spreading of the buoyant gas must be significant Spreading must occur on the timescale comparable to or shorter than the cooling timescale BUT Heating must be consistent with observations No convection Preserved abundance gradients Cool rims around rising bubbles Radio 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

3 C 84 and Perseus Cluster Fabian et al. 2000 Note multiple “fossil” bubbles, not aligned with current radio jets Chandra image

RAPID ISOTROPIZATION – buoyant gas spreads laterally on dynamical timescale until it covers steradians Ruszkowski, Kaiser & Begelman 2003

3 C 84 and Perseus Cluster Fabian et al. 2000 Cold rims, not strong shocks Chandra image

COOL RIMS – entrainment of lower temperature gas Ruszkowski, Kaiser & Begelman 2003

THE DEEPEST VOICE FROM THE OUTER SPACE Unsharp masked Chandra image X-ray temperatures 131 kpc Fabian et al. 2003

MEDIA CRAZE

SOUND WAVES Ruszkowski, Kaiser & Begelman 2003

3 C 338 and Abell 2199 Johnstone et al. 2002 “fossil” bubbles Chandra image +1. 7 GHz radio

Conditions emulate Abell 2199, with cooling; Ruszkowski, Kaiser & Begelman 2003 127 186 244 303 Myr

Radio: Higher contrasts, detectable only close to jet axis X-rays: spread out laterally 3 C 338 + Abell 2199 (Johnstone et al. 2002) “Ghost cavities” do not trace previous jet axis

CONCLUSIONS SEMI-ANALYTICAL MODELS • No need for large mass deposition rates • Minimum temperatures around 1 ke. V • Entropy floor NUMERICAL SIMULATIONS • • Significant and fast lateral spreading Sound waves Cool rims Mismatch between X-ray and radio emission