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Cooling Flows & Galaxy Formation. James Binney Oxford University. Outline. Cooling flows – historical introduction Current issues in CF dynamics Much work from Henrik Omma’s (05) thesis SEQUEL TOMORROW Implications for galaxy formation and BH growth. “Cooling flows”.

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cooling flows galaxy formation

Cooling Flows & Galaxy Formation

James Binney

Oxford University

  • Cooling flows – historical introduction
  • Current issues in CF dynamics
  • Much work from Henrik Omma’s (05) thesis


  • Implications for galaxy formation and BH growth
cooling flows
“Cooling flows”
  • Potentials of E galaxies & galaxy clusters filled with gas @ Tvir (106 – 108 K)
  • Detected in Xrays since early 1970s (forman et al 72; Mitchell et al 76)
  • First model (Cowie & B 1977) involved mass-conserving flow to centre
  • Predicted jX(R) inconsistent with Einstein images

Stewart et al 84

distributed mass drop out
Distributed mass drop-out
  • Consistency with measured jX(r) obtained by assuming ICM multiphase (Nulsen 86)
  • Field instability analysis implied runaway cooling of overdense regions (tcool/ 1/)
  • Cooler regions radiate all E while at rÀ 0
  • Predicts that there should be (a) cold gas and (b) line radiation from T<106K throughout inner cluster
g modes
G modes
  • Malagoli et al (87): overdense regions just crests of gravity waves
  • In half a Brunt-Vaisala period they’ll be underdensities.
  • Oscillations weakly overstable (Balbus & Soker 89) but in reality probably damped.
  • Conclude: over timescale <tcool heating must balance radiative losses
  • Systems neither cooling nor flowing!
agn heating
AGN Heating
  • AGN natural heaters
  • Cooling first becomes catastrophic @ centre
  • Where there’s a massive BH
  • Accretion onto BH will be sensitive to local gas
  • BH could heat through (a) Compton scattering (Ciotti & Ostriker 97, 01) or (b) jets
  • With point-like heat source expect generation of adiabatic core
  • In Tabor & Binney (93) growing core matched to CF envelope
  • In Binney & Tabor (95) jets episodically heat gas in distributed fashion
1993 2001
1993 - 2001
  • Distributed mass dropout still regarded as established fact in mainstream (Fabian 94)
  • Conflicts with observation finessed with epicycles:
  • Internal absorption (Allen & Fabian 97)
  • Magnetic locking (Tribble 89, Balbus 91)
  • Abundance anomalies (Fabian et al 01)
  • Conduction from large to small r (Bertschinger & Meiksin 86, Narayan & Medvedev 01)
2001 chandra xmm newton
2001 – Chandra & XMM-Newton
  • XMM doesn’t see lines of <106K gas
  • XMM shows that deficit of photons at <1keV not due to internal absorption
  • But associated with “floor” T' Tvir/3
  • Chandra shows that radio plasma has displaced thermal plasma

(Bohringer et al 02)

(Peterson et al 02)

bubble models churazov et al 2001 quilis et al 2001 brueggen kaiser 2001 2002 brueggen et al 2002
Bubble Models(Churazov et al 2001; Quilis et al 2001; Brueggen & Kaiser 2001,2002; Brueggen et al 2002)
  • Start with elliptical high-T cavity
  • Watch it rise
  • Cavity can’t be in pressure equlibrium with surroundings
  • The flow field around cavity dynamically important
  • Need for jet simulations

Churazov et al 01

injection models quillis et al 01 brueggen kaiser 02
Injection Models(Quillis et al 01, Brueggen & Kaiser 02)
  • Add thermal energy at some fixed off-centre location
  • Poor representation of effects of moving jet hot-spot

Brueggen & Kaiser 02

jet simulations
Jet Simulations
  • Early simulations 2D (Reynolds et al 02, Vernaleo 06)
  • Or on non-refined grids (Basson & Alexander 03)
  • Usually there’s a spherical boundary around the origin with free-flow condition
  • Omma et al (04) eliminated this boundary and had novel scheme for firing jets
omma s simulations
Omma’s Simulations
  • Simulations on 3d hydro with adaptive grids (Bryan’s code ENZO)
  • Entropy (no cooling)
  • Density (no cooling)
  • Entropy (cooling)
  • Density (cooling)
  • Key processes:
  • 1) Uplift
  • 2) Mixing
  • 3) Excitation of non-linear gravity waves
outward increasing entropy
Outward increasing entropy

Omma thesis 05

Donahue 04

current issues 1 enough e
Current Issues 1) enough E?
  • Probably Quasar mode & Radio-galaxy mode depending on whether accreting cold or hot gas (Binney 04, Croton et al 06)
  • In RG mode L¿ LEdd and ~all output mechanical (Virgo A prime example)
in m87
In M87
  • Chandra resolves rBondi
  • MBondi = 0.1 M¯/yr (Di Matteo et al 03)
  • So L = 5£1044 erg/s if 0.1mc2 released
  • LX(<20kpc) = 1043 erg/s (Nulsen & Boehringer)
  • LX(AGN) < 5x1040 erg/s
  • LMech(jet) = 1043 – 1044 erg/s (Reynolds et al 96; Owen et al 00)
  • So BH accreting at near MBondi & heating on kpc scales with high efficiency (Binney & Tabor 95)
current issues 2 the duty cycle
Current Issues2) the duty cycle
  • AGN known to be unsteady
  • Energy dissipated @ centre only if jet channels have quiet time (or jets precess) (Omma & Binney 04, Vernaleo & Reynolds 06)
  • Sometimes two generations of bubbles (Birzan et al 04)
  • Suggests inter-outburst time ~ rise time ~100Myr
  • E of outburst > 2.5PV of bubble
  • Suggests Lmech ~ LX
  • Actually Lmech may be significantly larger
Define cavities by <0/4
  • Evaluate PV
  • Peaks at only 10% of actual input

Omma 05

current issues 3 does mixing destroy z gradients
Current Issues3) does mixing destroy Z gradients?
  • Follow tracer dye from (a) r<5kpc, and (b) 5<r<77 kpc

Omma 05

effect on z gradient
Effect on Z gradient

Omma thesis 05

Boehringer et al 04

current issues 4 fixing the radial density profile
Current Issues4) fixing the radial density profile
  • For steady state, E(r) must match jX(r)
  • Why do clusters have similar jx profiles?
  • Effervescent heating? (Roychowdhury et al 05)
  • Damped sound waves? (Fabian et al 04, Ruszkowski et al 05)
  • Other physics? (Vernaleo & Reynolds 06)
omma binney 04
Omma & Binney 04
  • A more powerful jet disrupts further out
  • A more concentrated profile disrupts jet further in
  • Later jet ignition → bigger outburst
  • Later ignition → more centrally concentrated density profile
  • So later ignition ! strong, centrally concentrated heating
  • Start from present configuration of Hydra (David et al 2000)
  • Wait (i) 262 Myr (ii) 300 Myr
  • In (ii) extra 4x1059 erg lost to radiation, so add 8x1059 erg rather than 4x1059 erg as in (i)
  • EBondi=5(M/109M¯)2£1059erg in 262Myr; EBondi=7(M/109M¯)2£1059erg in 300Myr
Outbursts have undone 300 Myr of cooling
  • System with later ignition ends less centrally concentrated
  • Implies that systems can oscillate around an attracting profile
current issues 5 shocks
Current Issues5) Shocks
  • Unsharp-masked X-ray images show ripples (Fabian et al 03, 06; Forman et al 03)
  • Are these sound waves / weak shocks?
  • Expected T variations not seen (Fabian et al 06)
  • Or Gravity waves?
  • “Cooling flows” thermostated by AGN
  • This was predicted in early 90s
  • AGN are in “radio mode” and have high mechanical efficiency
  • They heat episodically via jets (non-adiabatic)
  • Central gas density regulates energy production
  • Profile of heat generation regulated by density profile of gas via radius of jet disruption
  • Nature of small-scale structures still unclear
cdm clustering
CDM Clustering
  • Small-scale cosmic web of DM develops around z~30
  • Subsequently larger-scale webs form from collapsed structures from earlier webs
  • Gradually accumulate superposition of halos with ~power-law mass function
  • Mass function unlike galaxy L function
galaxy formation
Galaxy Formation
  • Low M galaxies suppressed by photoionization, evaporation & SN feedback (Efstathiou 92; Dekel & Silk 86; Dekel 04)
  • Infalling gas shocks
  • Accretion shock near centre if tcool<tfree-fall
  • Condition holds for most mass in halos with M<1012M¯ (Dekel & Birnboim 03, 06)
lumpy accretion
Lumpy Accretion
  • Extended Press-Schechter predicts lumpy accretion (mergers/cannibalism)
  • Accretion shock unhelpful concept for lumpy accretion
  • So without SN heating all gas cold
sn heating
SN Heating
  • After starbursts SN heat much gas to ~107K
  • Flows out of halos with vc<100 km s-1 (Larson 74, Dekel & Silk 86)
  • In larger halos SN-heated gas accumulates
  • As infall continues, central density rises
  • Cannot be stabilized by SN heating
agn heating1
AGN Heating
  • tcool=3/2mpkT/n shortest @ centre
  • BH accretion rate rises with n0
  • Mechanical L stabilizes hot gas
  • In absence of cold infall hot gas cannot cool
cold infall
Cold Infall
  • Cold infall widely observed:
  • Magellanic stream
  • Perseus filaments
  • At hot/cold interface
  • (a) ablation by conduction/mixing (small blobs)
  • (b) condensation and star formation (larger blobs)
  • Conduction more important at high T (Nipoti & B 04)

Conselice et al 01

connection with bh growth
Connection with BH growth
  • BH growth known to take place in bursts:
  • Yu & Tremaine (2002) find (i) AGN have radiated in optical/UV as much E as released by all nuclear BHs; (ii) L~LEdd and ε>0.1 needed to produce observed quasars from observed BHs
  • @LEdd M~exp(t/tSalpeter); tSalpeter~25 Myr
  • So M from 103M¯ To 109M¯ with 14tS~0.4Gyr and 10Gyr at <0.05LEdd
  • Magorrian relation M~Mbulge, high α/Fe of bulges, high ages of bulges all imply LEdd (quasar) phase associated rapid star formation
  • Conjecture this is when there is cold gas @ centre
  • Episodes end when well deep enough to trap 107K gas; then Mdot 0.002 to 0.02 M¯/yr to offset 1043 – 1044 erg/s of LX
semianalytic gf croton et al 06 cattaneo et al 06
Semianalytic GF(Croton et al 06 & Cattaneo et al 06)
  • From model of DM clustering take merger history of halo population
  • Fraction 0.17 or 0.14 of M in baryons
  • Primary halos have hot gas, cold gas, stars
  • Secondary halos has stars & cold gas
  • They spiral in by dynamical friction
  • Bulges form in (a) merger-driven starbursts and (b) disk instabilities
  • SNe expel gas
cattaneo et al 06
Cattaneo et al (06)
  • Standard models:
  • Gas shock heated & arranged in singular isothermal sphere
  • Cools to exponential disk
  • dot M*=Mcool/(tdyn)
  • ½ dot Mwindve2=SNsnESNdot M*
  • Makes too many bright blue galaxies
  • Makes luminous galaxies too late
  • Lack of COMBO-17 red galaxies
new models
New Models
  • Sharp transition: cold infall ! virialization @ Mcrit=Mshock£ Min(1,101.3(z-zc)
  • At M>Mcrit reheat cold gas
  • Now dot M*=(1+z) Mcold/(tdyn)
  • Find '0.6, Mshock'2£1012M¯, zc'3.2
new models1
New Models
  • Good agreement global SFR
croton et al 06
Croton et al (06)
  • Gas shock heated to Tvir & cools to disk
  • Either immediately (rcool>rvir) or at rate 4(rcool)rcool2 drcool/dt
  • In disk steady SF at rate / (m-mcrit)/tdyn
  • SN inject energy ESN/m* to mass 3.5m*
  • When in hot halo gas has energy 3.5£0.5m*Vc2
  • Surplus E used to eject gas from halo
agn feedback
AGN Feedback
  • Croton et al follow mBH(t)
  • Mergers drive quasar mode: mBH=f mcold/[1+(280/Vvir)2] with f(msat/mhost)
  • No feedback
  • In radio mode dmBH/dt/ mBHfhotVvir3
  • LBH= c2(dmBH/dt) offsets radiative cooling
croton et al results
Croton et al Results
  • Feedback suppresses cooling at large Vvir and low z
  • Eliminates very luminous galaxies
  • Establishes red/blue dichotomy

Croton et al

Croton et al

  • Now clear that AGN heating important for GF
  • Distinguish quasar & RG modes
  • RG mode when dense atmosphere @ Tvir
  • RG mode only in massive halos
  • BHs grow principally from cold gas simultaneously with rapid SF in bulge
  • Gas at Tvir never forms stars – galaxies don’t form from cooling gas
  • Gravitational heating certainly unimportant at M<2£1012M¯
  • SN heating vital
  • Role of thermal conductivity/ablation to be clarified
heating cfs by bhs
Heating CFs by BHs
  • In absence of heating n(0)→∞ in t<tcool(0)
  • Such a cooling catastrophe must provoke a response from the central BH
bondi accretion
Bondi accretion
  • Area of sonic flow
  • Particle density
  • Accretion rate
  • Luminosity
  • So balance possible with E α ∫ dt LX
characteristic m 3x10 10 m kauffmann et al 03
Characteristic M*=3x1010M. (Kauffmann et al 03)
  • At M>M* dSB/dM=0; at M<M* dSB/dM>0
  • At M>M* galaxies old; at M<M* younger
  • At M>M* light centrally concentrated
theory of galaxy formation
Theory of Galaxy Formation
  • Standard picture: gas heated to Tvir on falling into Φ(Rees & Ostriker 1977; White & Rees 1978)
  • Actually fraction f enters at T<<Tvir(Binney 1977; Katz et al 2003; Birnboim & Dekel 2003)
  • f~1 on galaxy scales M* and below

Katz et al 02

Birnboim & Dekel 04