AGN jet launch scenarios

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1 AGN jet launch scenarios Rony Keppens Centre for mathematical Plasma Astrophysics Department of Mathematics, KU Leuven Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 1 / 48

2 Astrophysical Jets astrophysical jets: ubiquitous presence of accretion disks Young Stellar Objects (YSO) compact objects in binaries Active Galactic Nuclei (AGN) collimated, reach high velocities (up to c) mass source of the jet? how to collimate and keep collimated? how to launch and accelerate mass in jet? Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 2 / 48

3 Protostar environments Forming stars: T-Tauri with mass M M optical HST image (Burrows et al. 1996) edge-on flaring disk, reflection nebula, jets collimated emission-line jets from center jet-knots move at few hundred km/s (supersonic!) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 3 / 48

4 Link between accretion disk and jet? observed proportionality jet/disk luminosity Jet collimation: magnetic? Rotation measured at AU above disk Bacciotti et al 2002, Dougados: ApSS 293, 45 (2004) resolved v ϕ profiles O(10) kms 1, jet width 30 AU consistent with magneto-centrifugal launch Direct detection B in inner disk region FU Ori: Donati et al, Nature 438, 466 (2005) 1 kg field at 0.05 AU, T K, n m 3 significant ratio vertical/azimuthal field [O(2)], β = O(1)! role B in accretion, AM transport, disk/jet instabilities? Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 4 / 48

5 Link between accretion disk and jet? observed proportionality jet/disk luminosity Jet collimation: magnetic? Rotation measured at AU above disk Bacciotti et al 2002, Dougados: ApSS 293, 45 (2004) resolved v ϕ profiles O(10) kms 1, jet width 30 AU consistent with magneto-centrifugal launch Direct detection B in inner disk region FU Ori: Donati et al, Nature 438, 466 (2005) 1 kg field at 0.05 AU, T K, n m 3 significant ratio vertical/azimuthal field [O(2)], β = O(1)! role B in accretion, AM transport, disk/jet instabilities? Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 4 / 48

6 Magnetic Accretion-Ejection structure key ingredients are: presence of accretion disk + B observed versus artist impression (for AGN) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 5 / 48

7 Magnetic Accretion-Ejection structure key ingredients are: presence of accretion disk + B observed versus artist impression (for XRB SS433) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 5 / 48

8 Plotkin et al, MNRAS 2012 fundamental plane BH activity: link radio, X-ray luminosities, BH mass log L x = ξ R log L R + ξ M log M BH + B from galactic BH up to supermassive (BL Lac) AGN cores converting accretion flow energy to radiation is universal! Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 6 / 48

9 Casse & Keppens, ApJ 581, 988 (2002) perform axially symmetric 2.5D MHD simulations disk with initial vertical B: self-consistently forms collimated jet 15 % of accreted mass persistently ejected Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 7 / 48

10 MAES mechanism for jet launch and acceleration mass source: accretion disk collimation and acceleration of jet: B identical for YSO, compact objects, AGN MAES model: gravitational influence on disk material does not require specific disk/magnetosphere interaction object (+ magnetosphere or event horizon): point source consistent with observed jet radii at origin Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 8 / 48

11 MAES: Streamlines in jet launch region: accretion and ejection resistive disk treatment allows accretion accretion rate as BC: mimics outer regions Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 9 / 48

12 MAES: persistent launch spatio-temporal resistivity only in disk accretion flow slips across vertical B region above disk: ideal MHD (frozen-in) jet launch, once initiated, persists: material ejected from disk: 15 % of Ṁ A Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 10 / 48

13 MAES: hollow jets since jet launched from disk: hollow jet reaches super-fastmagnetosonic speeds accelerated while ejected, magneto-centrifugally Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 11 / 48

14 MAES: Force analysis Jet ejection mechanism: axial force analysis thermal pressure gradient lifts matter magnetic torque brakes in disk, spins up jet Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 12 / 48

15 Jet ejection mechanism: axial (vertical) force analysis thermal pressure gradient lifts matter out of disk at surface magnetic torque (J B) θ changes sign at disk surface: brakes disk matter, gravity wins from centrifugal: accrete spins up jet: magnetocentrifugal acceleration of jet matter AM is transported by magnetic field AM flux purely parallel to poloidal flow v p /B p configuration Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 13 / 48

16 Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 14 / 48

17 MAES: Angular Momentum Angular Momentum: channeled by B in disk: magnetic torque brakes azimuthally gravity wins from centrifugal: accretion AM flux parallel to poloidal flow/b p torque (J B) ϕ changes sign at disk surface: magnetocentrifugal acceleration of jet starts and stays collimated by magnetic hoop force B ϕ created by rotating disk Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 15 / 48

18 MAES Jet extent radial extension of jet launching region equipartition field region sufficiently bent poloidal B(cold jet) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 16 / 48

19 MAES Energetics Jet energetics: hot jet emerges disk material heats: compression & Ohmic jet luminosity energy liberated by accretion GM Ṁ A /2R I Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 17 / 48

20 MAES Summary Mechanism for launch: magnetic torque brakes disk material azimuthally and spins up jet mass source for jet: disk B collimates B accelerates Launching jets comoving view Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 18 / 48

21 Jet launching: improving the models Numerical proof of principle (2.5D VAC simulations) Jet Launch: ApJ 581, 988 (2002) Energetics: ApJ 601, 90 (2004) MAES model explains how jets are launched and accelerated why start and remain collimated underluminous disks and hot jets improvements: higher resolution (grid-adaptive) studies Zanni et al., A&A 469, 811 (2007) including stellar outflows, viscosity in the disk Meliani et al., A&A 460, 1 (2006) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 19 / 48

22 Zanni et al., A&A 469, 811 (2007) FLASH code (with AMR); emphasize role of anomalous resistivity prescription in disk (not always steady jet launch) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 20 / 48

23 Two-component outflows [Meliani et al.: A&A 460, 1 (2006)] turbulence by enhanced visco-resistive α-prescription Poynting flux of disc-jet: removes most AM from thin disc β 1 in disc scale height effective torque wind region: hot corona (turbulent heating near axis) numerical sink (0.1 AU) mass source along polar axis Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 21 / 48

24 Two-component outflows collimation differs for wind versus jet wind region forces: thermal + Lorentz (pinch) in turn collimated by disc-driven jet all axisymmetric, aimed at stationary endstates, unanswered: 3D jet stability and termination multi-component jets: interface dynamics? near star accretion dynamics or inner near BH regime Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 22 / 48

25 So far: considered how to launch jets, aided by B launch/propagation/termination should be studied jointly helically magnetized jets propagation hot jet, penetrating molecular cloud Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 23 / 48

26 observed fine structure along jet axis: shocks? MHD wave propagation for radio jets study m = 0 perturbations for compressible magnetic jet linear wave mode dispersion relation integrodifferential equation for weakly nonlinear waves: possible observed jet structure as evidence of soliton propagation along jet axis? Roberts, ApJ 318, 590 (1987) consider stability aspects for jet segment first Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 24 / 48

27 observed fine structure along jet axis: shocks? MHD wave propagation for radio jets study m = 0 perturbations for compressible magnetic jet linear wave mode dispersion relation integrodifferential equation for weakly nonlinear waves: possible observed jet structure as evidence of soliton propagation along jet axis? Roberts, ApJ 318, 590 (1987) consider stability aspects for jet segment first Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 24 / 48

28 observed fine structure along jet axis: shocks? MHD wave propagation for radio jets study m = 0 perturbations for compressible magnetic jet linear wave mode dispersion relation integrodifferential equation for weakly nonlinear waves: possible observed jet structure as evidence of soliton propagation along jet axis? Roberts, ApJ 318, 590 (1987) consider stability aspects for jet segment first Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 24 / 48

29 Jet variability (knots): internal or disk instabilities? non-straight: precess or deformed helically? Jet collimation: magnetically? Idealized studies in MHD framework Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 25 / 48

30 3D jet configurations [astrophysical] jet of radius R jet : 3D Kelvin-Helmholtz case study cylindrical cross-section shear flow (width 2a) across its circumference t = 0 parallel uniform B, V 0 = 0.645, a = 0.05, B 0 = reference parameters M s = 0.5, M a = 5, β = 120 3D perturbation wavenumber n along jet, m about jet axis sideways kink perturbation m = 1 = n Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 26 / 48

31 quasi-linear analytical prediction: (m, n) = (1, 1) excitation leads to (0, 2), (2, 2), and (2, 0) check for t < 0.5: poloidal magnetic/kinetic energy evolution Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 27 / 48

32 in horizontal cross-cut: doubled 2D result: ρ at t = 4 Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 28 / 48

33 high ρ isosurface and v x = 0 jet surface colored by p th Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 29 / 48

34 p th gradient induces wavenumber doubling on top/bottom Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 30 / 48

35 low ρ: 3D fibril and sheet structures: cospatial with high B pol Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 31 / 48

36 localized 3D high B pol regions control jet deformation Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 32 / 48

37 Nonlinear evolution for varying initial 3D perturbation field lines, density evolution Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 33 / 48

38 Kelvin-Helmholtz and Current-Driven modes 3D MHD simulations of cylindrical jets supersonic M = 1.26 jet segment with axial β = 32 unstable surface-type Kelvin-Helmholtz instabilities uniform B: nonlinear evolution as before astrophysical jet collimation azimuthal field components collimation by jet pinching (tension in B ϕ ) helical fields: current-carrying jets possibility for both KH and current-driven kink instabilities study interplay between KH and CD instabilities in jets Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 34 / 48

39 Magnetic Lorentz force = tension + pressure Flux tube with twisted field lines: stabilizing axial B Z tension destabilizing B ϕ pressure in kink pure MHD kink instability when twist q = B ϕ /RB Z > q cr Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 35 / 48

40 magnetized cylindrical jets axial flow profile V Z (R) tanh[(r j R)/a] 3 magnetic configurations: Uniform twisted fields For sufficiently twisted B fields: both KH and kink unstable what about their mutual interaction? Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 36 / 48

41 current-carrying HEL2 (highest twist) case: eigenfunctions linear radial displacements show different character ξ r m = 1 CD is localized centrally m = ±1 KH is localized at jet radius R = R j = 1 Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 37 / 48

42 saturation-disruption compare UNI (a), HEL1 (b), HEL2 (c) density structure in jet cross-section at t = 14 development fine structure less when twisted decrease of axial kinetic energy: less in HEL2 case Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 38 / 48

jet coherency maintained due to KH-CD interaction magnetic deformation due to centrally developing CD increases B ϕ & saturates KH vortices at jet surface 3D impression of jet

43 jet coherency maintained due to KH-CD interaction magnetic deformation due to centrally developing CD increases B ϕ & saturates KH vortices at jet surface 3D impression of jet after 14 transit times: UNI versus HEL2 increased (nonlinear) stability due to interacting instabilities! Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 39 / 48

44 Moll 09 non-relativistic 3D MHD jets, decay of toroidal field by kink Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 40 / 48

45 Rossi et al. 08 relativistic 3D HD jets, mix in ISM: entrainment self-consistent spine-layer develops (starts as underdense jet) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 41 / 48

46 Mizuno et al. 07 relativistic 3D MHD jets, with spine-sheath structure distortions from boundary perturbations when weakly magnetized, surrounding wind stabilizes Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 42 / 48

47 Jets (+disks) at galactic scales, with central supermassive BH what about relativistic to GR effects? close to BH: gravity wins, Bondi accretion (supersonic inflow, reverse of solar Parker wind) where inflow supersonic sets accretion radius rotation + AM conservation halts inflow (disk/torus forms) disk turbulence: α prescription for thin disk inner regions: radiation pressure can repel mass supply MHD processes needed for jet production: magnetocentrifugal (cold) jets: Blandford-Payne Blanford-Znajek: EM energy from rotating BH ergosphere Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 43 / 48

48 Jets (+disks) at galactic scales, with central supermassive BH what about relativistic to GR effects? close to BH: gravity wins, Bondi accretion (supersonic inflow, reverse of solar Parker wind) where inflow supersonic sets accretion radius rotation + AM conservation halts inflow (disk/torus forms) disk turbulence: α prescription for thin disk inner regions: radiation pressure can repel mass supply MHD processes needed for jet production: magnetocentrifugal (cold) jets: Blandford-Payne Blanford-Znajek: EM energy from rotating BH ergosphere Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 43 / 48

49 Jets (+disks) at galactic scales, with central supermassive BH what about relativistic to GR effects? close to BH: gravity wins, Bondi accretion (supersonic inflow, reverse of solar Parker wind) where inflow supersonic sets accretion radius rotation + AM conservation halts inflow (disk/torus forms) disk turbulence: α prescription for thin disk inner regions: radiation pressure can repel mass supply MHD processes needed for jet production: magnetocentrifugal (cold) jets: Blandford-Payne Blanford-Znajek: EM energy from rotating BH ergosphere Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 43 / 48

50 near BH structure: without/with accretion in plunging region [Komissarov, Ch. 4: Relativistic jets from AGN, Wiley, 12] Figure 4.5 The magnetic flux trapping effect. Left panel: Structure of the magnetosphere in the model where the disk is terminated at the last stable orbit. Right panel: Structure of the magnetosphere with included accretion flow in the plunging region (light shadow of grey ). Notice that in this case the magnetic flux threading the black hole is higher. Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 44 / 48

51 Meliani et al. 06 analytic stationary GRMHD solutions, Schwarzschild BH metric efficient magnetic rotator collimates to cylindrical jet by magnetic pinching, hot corona drives thermally, low Poynting flux, near axis solution by construction Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 45 / 48

52 Fendt 1997 numerical stationary GRMHD solutions, Kerr BH metric force-free electromagnetic solution: ρ c E + (1/c)j B = 0 gives cylindrically collimated, pure Poynting flux jet, internal force-balanced (finite element code) Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 46 / 48

53 McKinney et al, MNRAS 2012: 3D GRMHD for rotating BH density, field lines and fluxes on BH Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 47 / 48

54 McKinney et al, Science 2013: 3D GRMHD for rotating BH self-alignment between inner disk and BH spin axis, outer disk controls further jet out direction Rony Keppens (KU Leuven) Jet launch Nov. 2013, IAC winter school 48 / 48

Jet Stability: A computational survey

Jet Stability Galway 2008-1 Jet Stability: A computational survey Rony Keppens Centre for Plasma-Astrophysics, K.U.Leuven (Belgium) & FOM-Institute for Plasma Physics Rijnhuizen & Astronomical Institute,