Cooling flows and Galaxy formation James Binney Oxford University

Outline Phenomenology of CFs Phenomenology of CFs Physics of heating Physics of heating Standard galaxy formation Standard galaxy formation Galaxy formation revisted Galaxy formation revisted

collaborators Len Cowie Len Cowie Gavin Tabor Gavin Tabor Henrik Omma Henrik Omma Fathallah Alouani Bibi Fathallah Alouani Bibi Carlo Nipoti Carlo Nipoti Filippo Fraternali Filippo Fraternali

The phenomenon Thermal X-rays from Thermal X-rays from Clusters of galaxies Clusters of galaxies Groups of galaxies Groups of galaxies Individual galaxies Individual galaxies Perseus (Fabian + 03) Jetha + 07

Cooling times short short Usually T(0) < T( 1 ) by factor ~ 3 Usually T(0) < T( 1 ) by factor ~ 3 Jetha + 07

In absence of heating Field (1965): Cooling causes runaway growth of T differences Field (1965): Cooling causes runaway growth of T differences T will drop fastest where entropy is lowest T will drop fastest where entropy is lowest Malagoli et al (1987): This will centre because away from centre cool (overdense) regions will sink till they reach gas with the same specific entropy (cf Maller & Bullock 04) Malagoli et al (1987): This will centre because away from centre cool (overdense) regions will sink till they reach gas with the same specific entropy (cf Maller & Bullock centre expect cooling centre expect cooling catastrophe

Central accumulation? Is cold gas streaming into centre? Is cold gas streaming into centre? In general no because: In general no because: Absence of young stars, of whatever mass (Prestwich et al 97) Absence of young stars, of whatever mass (Prestwich et al 97) X-ray SB profile insufficiently peaked X-ray SB profile insufficiently peaked X-ray spectrum shows little gas at T<1/3 T 1 (Boehringer + 02, Peterson + 03) X-ray spectrum shows little gas at T<1/3 T 1 (Boehringer + 02, Peterson + 03) keV Boehringer + 02 Peterson + 03

@ the centre of Perseus Molecular gas detected Molecular gas detected By J=0,1,2.. Transitions of CO (Edge + 01, Salome + 06) By J=0,1,2.. Transitions of CO (Edge + 01, Salome + 06) By rotation-vibration transitions of H 2 (Hatch + 05) By rotation-vibration transitions of H 2 (Hatch + 05) Atomic gas detected in H  etc Atomic gas detected in H  etc Gas extends out in filaments Gas extends out in filaments Soft X-ray emission from around filaments (Fabian + 03) Soft X-ray emission from around filaments (Fabian + 03) Not rotating Not rotating Less gas (~4 £ M ¯ ) than expected if catastrophic cooling for Gyrs Less gas (~4 £ M ¯ ) than expected if catastrophic cooling for Gyrs Salome + 06

Heating Invariably a massive centre Invariably a massive centre Such objects host central BHs Such objects host central BHs And central non-thermal radio sources And central non-thermal radio sources The Bondi accretion rate onto BH is temperature-dependent The Bondi accretion rate onto BH is temperature-dependent So accretion rate rises steeply with falling T So accretion rate rises steeply with falling T

Evidence for mechanical heating First cavity seen in 1993 (Boehringer et al) First cavity seen in 1993 (Boehringer et al) Chandra sees many cavities (1999--) Chandra sees many cavities (1999--) Cavities often coincide with non-thermal radio emission Cavities often coincide with non-thermal radio emission

In M87 Chandra resolves r Bondi Chandra resolves r Bondi (Di Matteo et al 03) (Di Matteo et al 03) So L = 5 £ erg/s if 0.1mc 2 released So L = 5 £ erg/s if 0.1mc 2 released L X (<20kpc) = erg/s (Nulsen & Boehringer) L X (<20kpc) = erg/s (Nulsen & Boehringer) L X (AGN) < 5x10 40 erg/s L X (AGN) < 5x10 40 erg/s L Mech (jet) = – erg/s (Reynolds et al 96; Owen et al 00) L Mech (jet) = – erg/s (Reynolds et al 96; Owen et al 00) So BH accreting at fraction M Bondi & heating on kpc scales with high efficiency (Binney & Tabor 95) So BH accreting at fraction M Bondi & heating on kpc scales with high efficiency (Binney & Tabor 95)

Simulations Adaptive grid 3d hydro simulations Adaptive grid 3d hydro simulations Extended heat injection ! Extended heat injection ! realistic entropy profiles (Omma & Binney 05) realistic entropy profiles (Omma & Binney 05) Stress irreversibility of cavity creation (Binney et al 07) Stress irreversibility of cavity creation (Binney et al 07) Explain how heating statistically matched to cooling (Omma & Binney 05) Explain how heating statistically matched to cooling (Omma & Binney 05) V jet = 10,000 km/s Entr2kpc.mov V jet = 10,000 km/s Entr2kpc.movEntr2kpc.mov V jet =20,000 km/s \u\henrik\20kv\entr.mov V jet =20,000 km/s \u\henrik\20kv\entr.mov\u\henrik\20kv\entr.mov Omma thesis 05 Donahue + 05

Acoustic heating? Unsharp-masked X-ray images show ripples (Fabian et al 03, 06; Forman et al 03) Unsharp-masked X-ray images show ripples (Fabian et al 03, 06; Forman et al 03) Are these sound waves / weak shocks? Are these sound waves / weak shocks? Expected T variations not seen (Fabian et al 06) Expected T variations not seen (Fabian et al 06) Or gravity waves? Or gravity waves?

Summary Deep potential wells filled with gas at T vir Deep potential wells filled with gas at T vir Gas doesn’t cool: thermostated by AGN Gas doesn’t cool: thermostated by AGN Probably regulated by Bondi accretion of gas at T vir Probably regulated by Bondi accretion of gas at T vir Heating mechanical Heating mechanical Bubbles dynamical & only tips of icebergs Bubbles dynamical & only tips of icebergs

Galaxy formation Dark matter clusters from z ' 3000 Dark matter clusters from z ' 3000 Baryons cluster with DM from z ' 1000 Baryons cluster with DM from z ' 1000 At z~20 small regions start collapsing At z~20 small regions start collapsing On collapse gas shocked On collapse gas shocked In absence of cooling T ! T vir In absence of cooling T ! T vir

White & Rees (1978) ff CDM spectrum has much power on small scales CDM spectrum has much power on small scales So large fraction of baryons quickly collapse into small-scale halos So large fraction of baryons quickly collapse into small-scale halos CDM halos are cuspy, so survive on falling in to much larger halos CDM halos are cuspy, so survive on falling in to much larger halos So expect bulk of baryons to be in myriads of small galaxies So expect bulk of baryons to be in myriads of small galaxies In reality ~1/4 of baryons in galaxies, and most in L* ' M ¯ halos In reality ~1/4 of baryons in galaxies, and most in L* ' M ¯ halos Conclude: star formation suppressed in small halos Conclude: star formation suppressed in small halos

Suppression of SF On smallest scales: photoionization, evaporation (Efstathiou 92; Dekel 04) On smallest scales: photoionization, evaporation (Efstathiou 92; Dekel 04) On larger scales: SN feedback (Dekel & Silk 86) On larger scales: SN feedback (Dekel & Silk 86)

Trapped gas (Binney 2004) With standard IMF, SNe yield ~keV/particle ! T SN ~10 7 K With standard IMF, SNe yield ~keV/particle ! T SN ~10 7 K If T vir <T SN heated gas flows out If T vir <T SN heated gas flows out Once T vir >T SN it accumulates Once T vir >T SN it accumulates In classic semi-analytic models of GF ! “overcooling” and formation of many luminous blue galaxies (Benson et al 03) In classic semi-analytic models of GF ! “overcooling” and formation of many luminous blue galaxies (Benson et al 03) Actually most luminous galaxies belong to red sequence: no recent SF Actually most luminous galaxies belong to red sequence: no recent SF Baldry + 04 GD II M/L=220

GF by cooling? Galaxies of red sequence either have gas T vir (X-rays) or are subhalos of halos with T vir Galaxies of red sequence either have gas T vir (X-rays) or are subhalos of halos with T vir White & Rees (78), White & Frenk (91) assumed gas shock-heated to T vir on infall & GF occurred on cooling White & Rees (78), White & Frenk (91) assumed gas shock-heated to T vir on infall & GF occurred on cooling But CF data show trapped gas doesn’t cool! But CF data show trapped gas doesn’t cool! So how do galaxies form? So how do galaxies form?

Cold infall (Binney 2004) In simulations, higher resolution ! higher density ! faster cooling In simulations, higher resolution ! higher density ! faster cooling Dekel & Birnboim (03, 06) argued gas only heated when M>10 12 M ¯ Dekel & Birnboim (03, 06) argued gas only heated when M>10 12 M ¯ Corroborates results from clustering simulations (Keres + 05) Corroborates results from clustering simulations (Keres + 05) So blue-cloud galaxies can form from cold gas So blue-cloud galaxies can form from cold gas Inefficiently because T SN >T vir so M(eject)~M(SF) Inefficiently because T SN >T vir so M(eject)~M(SF)

Role of AGN Does AGN blast ISM away during a merger? Does AGN blast ISM away during a merger? Easiest at low M Easiest at low M So if ever possible, all galaxies would be red So if ever possible, all galaxies would be red AGN thermostats trapped gas to T vir AGN thermostats trapped gas to T vir

Onset of sterility Star-forming galaxies consume gas in less than t Hubble Star-forming galaxies consume gas in less than t Hubble E.g. MW: 2M ¯ yr -1 of SF consumes 4 £ 10 9 M ¯ in 2 Gyr E.g. MW: 2M ¯ yr -1 of SF consumes 4 £ 10 9 M ¯ in 2 Gyr Galaxies rejuvenated by infall of cold gas (NGC 4550) Galaxies rejuvenated by infall of cold gas (NGC 4550) Gas continuously replenished (HVCs; gas from Sgr dwarf, Magellanic Clouds etc) Gas continuously replenished (HVCs; gas from Sgr dwarf, Magellanic Clouds etc) Peek + 07 Putman + 03

Stopping Replenishment Atmosphere of trapped gas at T vir affects replenishment in 2 ways: Atmosphere of trapped gas at T vir affects replenishment in 2 ways: 1. Drag on infalling clouds 1. Drag on infalling clouds 2. Evaporation of cold gas 2. Evaporation of cold gas

Drag m c dv/dt=-A c  h v 2 ! v(t)=v 0 /(1+t/  )  =v 0 m c /A c  h m c dv/dt=-A c  h v 2 ! v(t)=v 0 /(1+t/  )  =v 0 m c /A c  h With R c <100 pc, v 0 =100 km s -1 and n h =10 -3 cm -3,  ' 300 Myr With R c <100 pc, v 0 =100 km s -1 and n h =10 -3 cm -3,  ' 300 Myr So clouds can’t move fast through halo So clouds can’t move fast through halo

NGC 5746 (Rasmussen + 07) Key transition object; v c =310 km s -1 Key transition object; v c =310 km s -1 Spherical halo unconnected to SFing disk Spherical halo unconnected to SFing disk

Extraplanar HI SF cycles gas through halo (HVCs; NGC 891; Fraternali & B 06) SF cycles gas through halo (HVCs; NGC 891; Fraternali & B 06) Extraplanar HI still rapidly rotating Extraplanar HI still rapidly rotating Not consistent with existence of n=10 -3 cm -3 non-rotating halo Not consistent with existence of n=10 -3 cm -3 non-rotating halo (Fraternali + B 07) (Fraternali + B 07) Fraternali + 05

Cored & Power-law Es Dichotomy in Es: (Faber , Ferrarese + 06) Dichotomy in Es: (Faber , Ferrarese + 06) Central SB slope  0.5 (PLGs) Central SB slope  0.5 (PLGs) PLGs: disky, M V >-20.5, large (v/  ) *, low L X /L B PLGs: disky, M V >-20.5, large (v/  ) *, low L X /L B PLGs younger centres PLGs younger centres What’s the connection between X-ray gas and stellar distribution? What’s the connection between X-ray gas and stellar distribution? Ferrarese + 06 Nipoti + B 07

Nipoti & B 07 N-bodies consistent with conjecture: when galaxies with BHs merge, remnant has core with M def ' M BH by upscattering (Milosavljevic & Merritt) N-bodies consistent with conjecture: when galaxies with BHs merge, remnant has core with M def ' M BH by upscattering (Milosavljevic & Merritt) Will be filled in by SF only if t evap >t dyn Will be filled in by SF only if t evap >t dyn t evap /t dyn smaller by 10 3 in X-ray luminous CG compared to PLG t evap /t dyn smaller by 10 3 in X-ray luminous CG compared to PLG So in PLG central SF possible after last merger So in PLG central SF possible after last merger

Summary Central BHs thermostat trapped gas at T vir Central BHs thermostat trapped gas at T vir Contradicts premise of White-Rees theory Contradicts premise of White-Rees theory Gas falls into low-M halos cold Gas falls into low-M halos cold SF drive outflow when T SN >T vir SF drive outflow when T SN >T vir At M~10 12 M ¯ (a) T vir ~T SN and (b) infall gravitationally heated to T vir At M~10 12 M ¯ (a) T vir ~T SN and (b) infall gravitationally heated to T vir So for M>10 12 M ¯ halos trap SN-heated gas So for M>10 12 M ¯ halos trap SN-heated gas

Summary (2) Galaxies in blue cloud while cold infall continues Galaxies in blue cloud while cold infall continues Galaxies transfer to red sequence when either (a) T vir >T SN or (b) fall in to halo with T vir >T SN Galaxies transfer to red sequence when either (a) T vir >T SN or (b) fall in to halo with T vir >T SN Because hot atmosphere kills cold infall by (a) drag on clouds (b) evaporation of clouds Because hot atmosphere kills cold infall by (a) drag on clouds (b) evaporation of clouds

Summary (3) Trapped gas almost non-rotating Trapped gas almost non-rotating So drag prevents infall feeding disk So drag prevents infall feeding disk After merger SF at centre of lower-L E possible After merger SF at centre of lower-L E possible Explains correlation of L X with optical properties Explains correlation of L X with optical properties