AGN Feedback In an Isolated Elliptical Galaxy

Transcription

1 AGN Feedback In an Isolated Elliptical Galaxy Feng Yuan Shanghai Astronomical Observatory, CAS Collaborators: Zhaoming Gan (SHAO) Jerry Ostriker (Princeton) Luca Ciotti (Bologna) Greg Novak (Paris) ; NAOC

2 Outline Observational evidences of AGN feedback Physics included in the model Numerical study of feedback Galaxy model Hydrodynamics Results and Conclusions

3 Observational evidence of AGN Feedback (I): (Fabian 2012, ARAA; Kormendy & Ho 2013, ARAA) Coevolution of AGNs and Their Host Galaxies MBH σ relation MBH Mbul relation Gultekin et al Sani et al. 2011

4 Observational evidence for AGN Feedback (II): High-mass end truncation of galaxy luminosity function Galaxy luminosity function Croton Springel et al. 2006

5 Other evidences Downsizing puzzle (Cowie et al. 1996) The most massive galaxies and BHs are the oldest Cooling flow problem in galaxy clusters (Peterson et al. 2001) Lack of significant cooling in cluster cores AGN heating may be the solution

6 Why AGN Feedback Important? --- Energetic argument The total energy emitted by the black hole during its growth: Etot=ε MBH c 2 The gravitational energy of a virialized sphere (e.g., the stellar bulge): The ratio is E M grav sph 2 * Etot/Egrav >>1

7 Jet/winds power larger than the cooling power of cooling flow For luminous clusters, groups, & elliptical galaxies. (Fabian 2012, ARA&A)

8 Two Key Issues How AGNs affect their host galaxies? -----interaction between radiation & wind with ISM How the AGN is affected by the host galaxy? ---black hole fueling

9 How Does SMBHs Get The Fuel? In galactic environment, gases are rotationally/thermally supported against gravitational collapse. Spirals: angular momentum transfer >> gas inflowing Ellipticals: (radiative) cooling flow >> gas inflowing (in our simulation, the gas all comes from the mass loss from stars) However, as the gas falls onto the galactic center, the density increases. Star formation could occur and consume lots of the gas before it is accreted by the SMBH, and so does galactic winds.

10 Two modes of AGN feedback Kormendy & Ho 2013, ARA&A Radiative (quasar) mode When L > 0.1 Ledd a standard thin disk Strong radiation; Strong wind; but no jet (but radio loud quasar?!) Kinetic (radio or maintenance) mode When L is low a hot accretion flow (Yuan & Narayan 2014, ARA&A) radiation weak, but spectrum different: no BBB; Both wind & jet

11 Two types of accretion models (I): cool disk Shakura & Sunyaev 1976, A&A; Pringle 1981, ARA&A Cool: ~10 6 K Geometrically thin Optically thick : photons will collide with gas particle many times before escape Spectrum: black body (or Planck) spectrum Radiative efficiency is high, ~0.1 A thin disk

12 Two types of accretion models (II): Hot Accretion Hot: ~10 12 /r (K ), Geometrically thick High radial velocity Optically thin Narayan & Yi 1994; Abramowicz et al Spectrum: complicated Radiative efficiency is lower; because the flow has no time to radiate before they fall onto the black hole Low-luminosity AGN, hard & quiescent state of BH X-ray binaries

13 Radiative efficiency of hot accretion flow Xie & Yuan 2012

14 For the most recent review of hot accretion flow, see: Feng Yuan and Ramesh Narayan, 2014, ARA&A, 52, 529 Hot Accretion Flows Around Black Holes

15 Mechanism of Wind Production (I): radiation-driven Murray et al. 1995; Proga et al. 2000; Liu, Yuan, Ostriker 2013 Require Line force Liu et al Proga et al Murray et al Probably in BAL quasar (quasar mode)?

16 Mechanism of Wind Production (II): magnetically-driven Yuan, Bu & Wu 2012; Narayan et al Early speculation (Narayan & Yi 1994; Blandford & Begelman 1999) The first self-consistent MHD simulation: Yuan et al At least for hot accretion flow (also works for cold disk!?)

17 Trajectory of ``test particles Yuan et al. 2014

18 Outflow confirmed by observations 3Ms observation to the quiescent state of Sgr A* by Chandra telescope H-like Fe Kα lines fitting flat density profile of accretion flow outflow Wang Yuan 2013, Science

19 The Fermi Bubbles Su et al Two giant γ-ray bubbles discovered by Fermi-LAT Morphology, Surface brightness, Spectrum

20 Our model: Inflated by accretion outflow Mou et al. 2014, ApJ Past activity of Sgr A* Mou et al Independent evidences: Mdot 10^4 times higher Still a RIAF Detailed numerical simulation Accretion rate consistent with other independent constrain Properties of outflow determined by MHD simulation of accretion flow Consistent with observations

21 Previous works on AGN feedback At large scale: ~100pc to several kpc; (Di Matteo et al. 2005; Debuhr et al. 2010, 2011; Johansson et al. 2009) only resolve galactic length and timescale At small scale: A few AU to ~1 pc: (Kurosawa & Proga 2009; Hopkins & Quataert 2010; Liu, Yuan, Ostriker et al. 2013): only resolve the BH accretion length and timescales, so accretion rate is taken to be given

22 Goal of our work: Resolve both the accretion and galaxy scales Resolve both the accretion and galaxy evolution timescales

23 Galaxy Model We focus on the cosmological evolution of an isolated elliptical galaxy. Gas source Stellar mass loss during the cosmological evolution Gravity Super massive black hole Stellar population Dark matter halo Interstellar medium? BH Stars Dark Matter

24 Hydrodynamical Equations

25 Setup of Numerical Simulation ZEUS code: 2D + hydro + radiation From 2.5 pc (< Bondi radius) to 250 kpc Evolve for cosmological time (several Gyr) Inject wind & radiation from the inner boundary & calculate their interaction with ISM LBH self-consistently determined

26 Contribution of supernovae (Ia type) to energy Ciotti, Ostriker et al Massive stars (SNe II) died before the simulation starts due to their short lifetime. But SNe Ia can be triggered by accretion or merger events of neutron stars/white dwarfs, 1.1 L t RSN( t) h yr L B,sun 13.7 Gyr 12 2 B 1 Each SN Ia releases energy in an order of 10^51 erg! But SN Ia only play its role (producing wind) at the outer region of the galaxy. In the inner region, AGN is more important.

27 Star Formation We estimate SFR using the standard Schmidt- Kennicut prescription:, max(, ) form * form cool dyn form We also consider SNe II among the newly formed stars. N II dn 1 M M M M dm M II dm x M M M M II x inf sun * 3 * inf sun sun

28 Radiation Heating & Cooling Sazonov et al Net energy change rate per unit volume: Bremsstrahlung cooling S Compton heating/cooling 35 S ( TX T) photoionization heating, line and recombination cooling S M 3 = n 2 (S 1 + S 2 + S 3 ) 27 T a b( / ) 10 c 23 0 c 1 ( / 0)

29 Compton temperature Compton heating ~ (Tc TISM) Definition of Tc In radiative (quasar) mode: Tc ~ 10 7 K In kinetic (radio) mode (Yuan, Xie & Ostriker 2009) Tc ~ 10 9 K But in all previous works, Tc is taken to be constant Ho 2008 ARA&A

30 Radiative transfer Why? To calculate Compton heating/cooling & photoionization How? di ds k I j ( ) di k k I j dr c p b

31 Length and timescales Bondi radius of hot gas: ~5 pc Galactic length scale: kpc Smallest cell: 0.2pc Accretion timescale: 10^4 yr Stellar evolution timescale: 10^9 yr

32 From the grown of BH: 10 4 < ε w < 10 3

33 Feedback loop Before outburst During outburst After outburst

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35 AGN duty cycle (I)

36 Importance of radiative feedback Top: ε w is constant Bottom: ε w decreases with M Blue: T c = 10 7 K Red: T c = 10 7 & 10 9 K in kinetic mode Conclusion: when ε w decreases with M which is realistic, radiative feedback in kinetic mode is very important

37 AGN duty cycle (II)

38 Star formation Blue: Tc constant; strong star formation Red: Tc varies, suppressed star formation

39 Conclusions The AGN feedback by both radiation and wind/outflow are considered by 2D numerical simulation Physical processes like supernovae, star formation, interaction between radiation & wind with ISM are considered The final mass of the BH is in reasonable agreement with observation Duty-cycle consistent with observation In kinetic mode, radiative feedback, which was thought not important, is actually equally important with mechanical feedback

40 END