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Does AGN “Feedback” in Does AGN “Feedback” in Galaxy Clusters Work?Galaxy Clusters Work?
Dave De Young
NOAO
Girdwood AK May 2007
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AGN Outflows (“Feedback”)AGN Outflows (“Feedback”)
Relevant to Galaxy Formation and Evolution
Relevant to Evolution of the Intracluster Medium and BCGs
Can Provide Information on Unknown Parameters of AGN Formation and Evolution
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Galaxy Formation and Galaxy Formation and EvolutionEvolution
Millennium Simulation
1 x 10 Particles; 500 Mpc10 3
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Galaxy Formation and Galaxy Formation and EvolutionEvolution
Bower et al. 2003
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Galaxy Formation and Galaxy Formation and EvolutionEvolution
– Effects of Radio AGN
Croton et al. 2006
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Evolution of The Intracluster Evolution of The Intracluster Medium and BCGsMedium and BCGs
Central Cluster Galaxies Should Now be Accreting ICM, Forming Stars (CDM)
Not Seen– Massive Elliptical Galaxies in Clusters are Old
and Red– No Evidence of Significant Star Formation in
Central BCGs
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Evolution of The Intracluster Evolution of The Intracluster Medium and BCGsMedium and BCGs
ICM Cooling Times < Hubble Time in Cores– Inflow Rates Up 100 M(solar) /yr– Not Seen– “Cooling Flow” Problem
Reheating by Cluster AGNOld Idea (~ 1970s) : Total Energies Suggestive
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AGN OutflowsAGN Outflows
Key Issue: Coupling of AGN Outflow to Surrounding Medium– Requires Understanding of the Interaction of
AGN Outflows with the Ambient Medium– Exchange of E, M, p– May Constrain Outflow Parameters (v, , )
if Ambient Medium, Interaction Known
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Radio Source Bubbles and Radio Source Bubbles and Cooling “Flows”Cooling “Flows”
Total Radio Source Energies (pdV) Are a Significant Fraction of ICM Energy Budget– Need to Convert Kinetic and Particle Energy
into HeatVia Turbulent Mixing with ICMVia Advection and Mixing of ICMVia Shocks in ICM
– Is There Enough Time to Do This?
(cf. B. McNamara)
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Models of Buoyant Radio Models of Buoyant Radio Source BubblesSource Bubbles
2-D Hydrodynamic
Abundant
Mixing!
X-Y High Resolution
Brueggen & Kaiser 2002
Density
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Models of Buoyant Radio Models of Buoyant Radio Source BubblesSource Bubbles
3-D Hydrodynamic
– Fragmentation, Mixing
Ruszkowski, Bruggen, & Begelman 2004
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Self Consistent Global Mixing Calculation Not yet Done.
But It’s Suggestive…
However…
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Relic Sources in ClustersRelic Sources in Clusters
N1275
Intact!– At Times >> t
Fabian et al. 2002
instab
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Consequences of Relic Radio Consequences of Relic Radio SourcesSources
Role of Magnetic Fields:– Does Bubble Expansion Creates Stabilizing Sheath?
Linear Stability Analysis:– At r ~ 50 kpc, n = 0.01, B = 3 x 10 G:– R-T: l = 13 kpc, t = 7 x 10 yr – K-H: Stable for U ~ 0.1 c
Possible Suppression of Fragmentation or Mixing for a Significant Fraction of Buoyant Risetime
-6
7
s
O O
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Current MHD CalculationsCurrent MHD Calculations
Time Dependent Evolution of Buoyant Radio Relics in a Stratified ICM – Look At:
R – T InstabilityLifting and Mixing of Different Elements of the ICMDestruction of Relic and Mixing with ICM
Includes Effects of Central Galaxy + Cluster Includes Inflation of Radio Relic Bubble
( With T. W. Jones, S. O’Niell)
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Initial & Boundary ConditionsInitial & Boundary Conditions
Gravitation – Includes Dark Matter– Central Galaxy
– King Model; Mc = 3 kpc; M = 3.5 x 10(12) Mo at 20 kpc
– Cluster– NFW Model; alpha = 0; M = 3.5 x 10(10) Mo at 10 kpc– Cluster Core = 400 kpc; M = 3.5 x 10(12) Mo at 50 kpc
ICM – Equilibrium Configuration– Isothermal – T = 3 keV = 3.5 x10(7) K – Density n = 0.1 at z = 5 kpc
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Initial & Boundary ConditionsInitial & Boundary Conditions
ICM – Equilibrium Configuration– Magnetic Field
Orientation: Phi = 0, 45, 90B = const or Beta = const (120 – 75K) |B| = 0.2, 1, 5 MicroGauss (Beta = 7.5(4), 3(3), 120)
Bubble R = 2 kpcP = Pext at z = 15 kpcn = 0.01n at z = 15 kpc Inflation time ~ 10 MyrdE/dt ~ 10 (42) erg/s
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Relic Radio Bubble EvolutionRelic Radio Bubble Evolution
Beta = 3000Bo = 1 Microgauss Internal B Parallel at Top
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Relic Radio Bubble EvolutionRelic Radio Bubble Evolution
Beta = 120
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 3000– Same Initial
Conditions as
2D Cases
Bubble MaterialVolume Rendered
t = 12.5 Myr
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 3000
t = 75 Myrt = 150 Myr
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 3000
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 120 bubble only
t = 75 Myr
t = 150 Myr
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 120
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Consistency with Consistency with ObservationsObservations
= 120
= 3000
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Next …Next …
Really
Tangled
Fields
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Bubbles with Tangled Interior Bubbles with Tangled Interior FieldsFields
– Beta = 120– t = 75 Myr
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Bubbles with Tangled Interior Bubbles with Tangled Interior FieldsFields
– Beta = 120– t = 75 Myr
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Conclusions – AGN Outflows and Conclusions – AGN Outflows and Reheating of the Ambient MediumReheating of the Ambient Medium
Radio Lobe Interaction with a Magnetized ICM Indicates:– Delay of Onset of Destructive Instabilities– Longer Times for Mixing with the ICM– Bubbles Decelerated, Evolution Subsonic– Volume of Lifted ICM Limited to Wake
Region Repeated Outbursts and/or Additional
Mixing Mechanisms May be Needed to Reheat the ICM
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Conclusions – AGN Outflows and Conclusions – AGN Outflows and Reheating of the Ambient MediumReheating of the Ambient Medium AGN Reheating Needed in CDM Galaxy
Formation Common FR-I Outflows May Show Strong Local
Coupling– Self Consistent Heating Rates not Yet Calculated
AGN Outflows in Clusters – Stop Cooling Flows?– Hydro Calculations Suggestive– Relic Radio Source Cavities Intact and Suggest
Interaction with a Magnetized ICM
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Consequences of B FieldsConsequences of B Fields
For Cluster ICM Reheating– Onset of Instability and Mixing Delayed– Initial Scale Length Large: l ~ 10 kpc
Mixing Time to Reheat Will Be Long - Time Required for Turbulent Cascade to Go From
Energy Range to Dissipation Range
– l /v ~ 3 x 10 yr
o
o turb
7
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Other Possible Heating Processes Other Possible Heating Processes Due to Radio Sources Due to Radio Sources
Sound Waves? Shock Waves?
Fabian et al. 2005
P/P
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Impact of Radio Source Impact of Radio Source CavitiesCavities
Complex ICM Structure – Centaurus Cluster
Fabian et al. 2005
0.4 – 7 keV + 1.4 GHz
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Other Possible Heating Processes Other Possible Heating Processes – Shock Waves– Shock Waves
Shock Waves:– Must be Supersonic
Sound Speed ~ 10 T Bubble Expansion Speed > 10 cm/s
– Likely to be Weak and Short LivedT* /T M, so T Not LargeBubbles Currently SubsonicVolume Heated Will be SmallDamped Shocks Become Sound Waves
– Thus a Local Phenomenon
4
8
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Other Possible Heating Processes Other Possible Heating Processes – Dissipation of Sound Waves– Dissipation of Sound Waves
Dissipation of Sound Waves– Some Models Assume pdV Energy Dissipated
in Cluster Core– Others – Approximate Dissipation (no B, no
Thermal Conductivity, Incompressible)L (3/8 ) c / ~ 100 kpc
Issue Not Yet Clear– How Much?– How Long?
2 2
Ruszkowski et al. 2004
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Non-Linear R-T InstabilityNon-Linear R-T Instability t = 0
Beta = 1.3 M Beta = 1.3 K 130 ~ ICM
1 kpc slices T = 10M K t = 15 Myr
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Prior MHD CalculationsPrior MHD Calculations
2-D MHD – Pre-formed BubbleTangential Field Inserted “By Hand”
Self Consistent MHD (Robinson et al. 2004)
Breuggen & Kaiser 2001
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Relic Radio Bubble EvolutionRelic Radio Bubble Evolution
Bubble
Deceleration
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Lifting and MixingLifting and MixingBeta = 120K OptimallyCoupled
Ambient ICM
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Relic Radio Bubble EvolutionRelic Radio Bubble Evolution
Beta = 3000Bo = 1 Microgauss; Internal B Antiparallel at Top
12.5 Myr
75
125
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Relic Sources in ClustersRelic Sources in Clusters 200 kpc Cavities (McNamara et al. 2005)
– MS0735– Z = 0.22– pdV ~ 10 erg
62
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Initial ConditionsInitial Conditions
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Properties of Radio Source Properties of Radio Source Cavities and ShellsCavities and Shells
Morphology– Limb Brightened, “Relaxed” Structure– NOT Head-Tail or “Normal” FR-I – Small/No Jets, but t ~ 10 yr– Tens of kpc in Diameter
Inferred Properties– In Pressure Equilibrium– Moving Subsonically (no Shocks)– Shell and Surroundings Cool– Buoyant Bubbles
7syn
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Relic Radio Bubble EvolutionRelic Radio Bubble Evolution
Beta = 3000Bo = 1 Microgauss Internal B
Anti-parallel at Top
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Three Dimensional MHD Three Dimensional MHD CalculationsCalculations
= 75000
Bubble Only - Volume Rendered
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Models of Buoyant Radio Models of Buoyant Radio Source BubblesSource Bubbles
3-D Hydrodynamic
Density8 Myr 25 Myr 41 Myr 59 Myr
Brueggen et al. 2002
10 x 10 x 30 kpc
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Evolution of The Intracluster Evolution of The Intracluster Medium and BCGsMedium and BCGs
Related to Previous Problem in ΛCDM Cosmology Models
Large ΛCDM Halos Form Late, Correspond to Massive Clusters
Z = 0, M/L = Const
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