Localisation of Non-thermal Emission Production Sites in AGN. Andrei Lobanov Max-Planck-Institut für Radioastronomie, Bonn

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1 Localisation of Non-thermal Emission Production Sites in AGN Andrei Lobanov Max-Planck-Institut für Radioastronomie, Bonn

2 Jet (Changing) AGN Paradigm A. Lobanov The BLR is a multicomponent complex Jet and so is the NLR There are also these things called corona Accretion disk Jets are everywhere BH Torus and they affect almost everything as well as the torus and ergosphere but jets are probably not formed and launched the way we presently think they are

3 A. Lobanov High Energy Emission in AGN High-energy emission production in AGN is believed to be related to relativistic particles (e ±, p) accelerated in jets. Exact locations of the HE/VHE production sites and the relative importance of leptons and hadrons are matter of ongoing debate. Limited resolution precludes direct localisation of the HE/VHE sites. Indirect localisation is done primarily via SED modelling (spectral domain) and multiwavelength variability campaigns (temporal domain). VLBI observations of radio emission add spatial domain to the localisation, by resolving individual radio emitting regions and relating their properties to the variable HE/VHE emission.

4 Spatial Localisation. Why? A. Lobanov Single zone leptonic/hadronic models are often insufficient to explain the entire broad-band spectrum or differences between faint and flaring states in AGN. Ample evidence exist for HE/VHE continuum to be generated in more than one location. Opacity and time delays may also need to be taken into account, which requires good spatial localisation. W Comae Leptonic model Hadronic model Böttcher & Bloom 2000 Böttcher, Mukherjee, Reimer 2002

5 Localisation with VLBI A. Lobanov VLBI observations now provide a ~50 mas resolution at 3 mm, resolving sub-parsec scale regions in all AGN and reaching down to scales of ~100 Rg in nearby AGN. Monitoring of individual regions traces in detail their kinematic and emission evolution this evolution can be related to variability of HE/VHE emission. 3C345, z=0.594 optical image X-ray image separation of jet features from the injection point trajectory of a jet feature 1 pc Schinzel et al Lobanov & Zensus 1999

6 Relativistic Outflows in AGN

7 Black Holes, Jets and AGN A. Lobanov Jets are formed in the immediate vicinity of SMBH. VLBI measurements probe scales of ~10R g and will go to ~1R g scales in the coming decade. 0.1 mas, VLBI at l=7mm 5 RS 0.2 mas in M87

8 Relativistic Flows in AGN A. Lobanov Launching Region: The Accretion Flow; ~ Rg (0.5 5 mpc; 5 50 mas) Probably unresolved or slightly resolved MHD Acceleration/Collimation Region: ~ Rg (1 < 100 mpc; 10 mas < 1 mas) The Jet Nozzle Transition Region: ~10 3 Rg (< 0.1 pc; < 1 mas) Poynting-Flux-Dominated (PFD) KFD Kinetic-Flux-Dominated (KFD) Jet: ~ Rg ( pc; 1 mas 20 ) Hot Spot/Lobe: ~10 9 Rg (~100 kpc; or 20 ) Outer jet is Kinetic-Flux-Dominated For a 10 9 Msun black hole at a 20Mpc distance ~ M87(Virgo A)

9 VLBI Core : Compact Jet A. Lobanov Location at which jets become visible in radio is most likely determined solely by the t=1 condition for synchrotron emisson (Königl 1981). 3C345 Nuclear flares can be described by relatively modest and smooth variations of particle density. Magnetic fields are either tangled or organized on scales much smaller than the resolution limit. Lobanov & Zensus 1999

10 Core Shift A. Lobanov Position offset of the optically thick core of a VLBI jet can be used to estimate physical conditions in the nuclear region of AGN Core offset measure: Derived magnetic field and distance from the central engine to the core: from core shift 3C345 Lobanov 1998

11 A. Lobanov Collimation and Acceleration VLBI observations of compact jets in nearby AGN provide strong evidence for collimation on linear scales of ~10 3 Rg and strong acceleration on parscec scales (~ Rg) M 87 Cyg A 230 Rs Krichbaum et al Bach et al Magnetically driven acceleration is a viable explanation for the observed speeds (Vlahakis & Königl 2004)

12 Shock-Dominated Regions A. Lobanov Strong shocks are present in jets on scales of several decaparsecs( Rg) revealed by polarization of radio emission and distribution of the synchrotron peak frequency. J1 3C 273 v app 5c J2 Core J1 Core J2 Lobanov et al. 1997

13 A. Lobanov Shocks and K-H Instability Shocks dissipate rapidly at distances of >10 7 Rg, giving way to Kelvin-Helmholtz instability as the major factor determining the morphology and dynamics of the flow. The instability develops in a non-linear regime Gj=2.1 Numerical 3D RHD simulations Gj=2.5 Wavelengths of the modes: l Hs =18.0, l Es =12.0, l Eb1 =4.0, l Eb2 =1.9 [mas] Jet parameters: G j =2.1, M j =3.5, h=0.02, a j =0.53, v w =0.21c Perucho et al Gj=3.0

14 A. Lobanov Instabilities on Large Scales Kelvin-Helmholtz instability determine the morphology and dynamics of jets on scales of Rg. But things are not always so simple... M87 TeV emission? v w =0.5c HST D E G I A B C Lobanov, Hardee, Eilek 2003

15 Non-Thermal Optical and X-ray Emission

16 Broad Lines in 3C390.3 A. Lobanov 3C390.3 shows strong, double-peaked broad lines. The blue- and redshifted peaks show complex kinematic behavior, and the velocity difference Vred Vblue is anticorrelated with the continuum and line flux; different continuum-line delays at the minimum and maximum of the continuum. -- two kinematically independent components? continuum blue wing red wing Vred - Vblue Shapovalova et al. 2000

17 Is BLR Connected to Jet? A. Lobanov Using VLBI observations to relate structural changes in the jet to optical variability in 3C390.3 Linear fits to component separations yield epochs of ejection from the central engine D and passages through the stationary region S1 Tavares 2009, Arshakian et al. 2010

18 Jet Optical Continuum A. Lobanov Two different line components in broad-line emission in 3C390.3 and are driven by two different continuum radiation sources located near the accretion disk (D) and in the jet (S1). S1 is a stationary formation (possibly a recollimation shock or acceleration end zone). W Hb = 10000, km/s t cont-line = 30, 100 days M bh = 4x10 8 M sol, 2x10 9 M sol Arshakian et al. 2010

19 A. Lobanov Optical and Radio Variability Flaring component of the optical continuum is associated with the stationary region S1 located in the jet, at a ~1.3 pc distance from the putative central engine of 3C390.3 Optical continuum flux Radio flux D Radio flux S1 Arshakian et al. 2010

20 The Story of 3C120 A. Lobanov 3C120: The same relation between optical flares and passages of jet components through a stationary region located at about 1.3 pc from the jet origin. VLBI data are too sparse to make any conclusions about variability of radio emission. However, apparently an orphan radio flare is detected in 2007 that is not immediately visible in the optical light curve. Tavares et al. 2010

21 X-ray Continuum A. Lobanov Ejections of new jet features are correlated with characteristic dips in the X-ray light curve likely due to disappearance of the inner part of the accretion disk. 3C390.3: Arshakian et al C120: Marscher et al. 2002, Chatterjee et al. 2009

22 Radio/Optical/X-ray in 3C120 A. Lobanov Joint modelling of radio, optical, and X-ray data in 3C120: radio flares and X-ray dips seem to originate near the accretion disk; optical flares are related to the region S1 located about 1.3 pc downstream. Chatterjee et al. 2009: X-ray, 43 GHz VLBI, and 37 GHz total flux density data Tavares et al. 2010: Optical and 15 GHz VLBI data Jet acceleration modelling following the MHD acceleration model of Vlahakis & Königl 2003 Nuclear opacity and absolute geometry of the jet is determined from the core shift, according to Lobanov 1998.

23 Radio-loud AGN A. Lobanov In radio-loud AGN, relativistic jets may power a BLR associated with a subrelativistic outflow from the nucleus. Relativistic jet VLBI core? Corona? Subrelativistic outflow BLR 2 (outflow) BLR 1 (disk) Optical (flaring) continuum BLR 2 is a non-virialized complex. This must be taken into account in BH mass estimates made from broad line widths. X-ray continuum VHE g-ray continuum?

24 g-ray Emission

25 The g-ray Connection A. Lobanov Early EGRET detections of AGN did not allow for detailed studies of broad band relations in individual objects However, in some cases, it was possible to relate g-ray detections to optical and radio flares and appearances of new jet features. Otterbein et al C g-ray? VLBI jet J

26 S [Jy] The g-ray Connection A. Lobanov jet component evolution + evolution of radio spectrum Lorentz factor, Gj = 11.8 Viewing angle, qj = 3.2 deg Doppler factor, dj = 16.4 Opening angle, fj = 2.1 deg Magnetic field, Bcore = 0.2 G optically thick region of jet modelled size and location of the jet component g-ray flare occurred in the VLBI core, at ~10 3 Rg Otterbein et al. 1998

27 Fermi/VLBI studies A. Lobanov Early Fermi/VLBI results: shocks in compact jets are likely source of short gamma-ray flares. Origins of longerterm variability are not clear: VLBI core? Underlying flow? Radio/Gamma sky 3C273, 3C279: radio emission from VLBI does not correlate with g-rays : VLBI core traces g-rays Jorstad et al. 2010

28 Jet g-ray Continuum A. Lobanov The g-ray emission in 3C345 is generated in a region of the jet of about 10 pc in extent, with individual flares likely associated with shocks moving through this region of the jet. The moving features also show a strong acceleration over this region. g-ray VLBI Q9 Q10 underlying trend in g-ray emission g-ray flares Schinzel et al. 2010

29 Localisation of TeV Emission

30 Some VHE g-ray Models A. Lobanov Black hole magnetosphere accelerating particles via Blandford-Znajek process, with an ADAF disk to reduce opacity for g-ray photons: VHE emission via synchrotron or IC. Expected location: 10 3 Rg Hadronic models (e.g., Reimer et al. 2004): injection of relativistic electrons and high-energy protons. VHE emission from synchrotron m ± /p ± radiation or by proton synchrotron. Expected location: Rg Leptonic jet models (e.g., Lenain et al. 2008, Tavecchio & Ghisellini 2008): essentially a two-flow jet, with VHE via synchrotron and IC from a fast spine, and radio emission via synchrotron from a slower sheet. Expected location: 10 5 Rg. Jet base/standing shock (e.g., Marscher et al. 2008): passage of relativistic plasma condensations through the jet base or a standing shock (i.e. recollimation shock) in the jet.vhe emission via synchrotron and IC. Expected location: 10 4 Rg, for the jet base, 10 6 Rg, for standing shock.

31 VHE in M87: Core or HST-1? A. Lobanov Evidence for short term VHE flares in the core and longer-term VHE variability from HST-1 (~100 pc away from the nucleus!) Cheung et al Acciari et al. 2009

32 Spatial Localisation A. Lobanov The size of 43 GHz core in M87 as used in Acciari et al corresponds to ~600 Rg, thus potentially favoring magnetospheric and hadronic models. However a more accurate localisation is needed here (as well as better understanding of the physics of radio-tev relation suggested for HST-1). A case for higher-frequency VLBI and for studies of Sgr A*, where the linear scale is about 2.5 times more favorable. There VLBI can help improving the present localisation and support the proposed localisation using stellar occultation. Localisation of VHE in Sgr A* region Acero et al Abramowski et al. 2010

33 Towards the Event Horizon A. Lobanov VLBI observations at 230 GHz (1.3 mm) probe a 4R S scale in Sgr A* VHE localisation by relating rapid VLBI and VHE variability. observed size: Central region in Sgr A* HHT - Carma 43 (+14/-8) mas deconvolved: 37 mas (3.7 R S ) Gaussian size: 43 mas Ring (doughnut) outer diameter: 80 mas inner diameter: 35 mas Doeleman et al Carma - JCMT HHT - JCMT Observed size from new 1.3mm VLBI observations 3.7 R S image credit: S. Noble (Johns Hopkins), C. Gammie (University of Illinois)

34 IACT & VLBI at 43+ GHz? A. Lobanov Majority of extragalactic VHE g-ray sources are detected with VLBI at 43 and 86 GHz. New 3mm VLBI survey: 144 hours of observing time; will focus on VHE g-ray sources. Targeted followups with intensive IACT / VLBI campaigns would be a very effective tool to localise and study VHE g-rays in AGN. imaged with VLBI at 3mm

35 Summary A. Lobanov High-resolution radio observation with VLBI offer an effective tool for localising the sites of continuum emission production in AGN. Jets are likely to be responsible for a large fraction of flaring continuum, from the optical to VHE g-ray bands. Accurate spatial localisation of VHE g-ray emission can be achieved with joint IACT and VLBI observations at 43+ GHz. This makes a strong case for seeking closer co-operation between VLBI and VHE instruments.