Active Galactic Nuclei: Jets and other Outflows To discuss two aspects of AGN Activity (About phenomena on parsec & kpc Scales) To discuss two aspects of AGN Activity (About phenomena on parsec & kpc Scales) Gopal Krishna NCRA-TIFR, Pune, INDIA Paul J. Wiita GSU, Atlanta, USA KASI-APCTP Joint Workshop (KAW4), Daejeon, Korea (May 17-19, 2006)

Three topics Peculiar radio (synchrotron) spectrum: S   1/3 Peculiar radio (synchrotron) spectrum: S   1/3 Electron energy spectrum: either mono-energetic, or having a low energy cut-off (LEC) Salient examples : Galactic (Sgr A* and the "ARC") Galactic (Sgr A* and the "ARC") Extragalactic (extreme IDV quasar PKS ) Extragalactic (extreme IDV quasar PKS ) Possible implication of LEC for the bulk motion of quasar jets Possible implication of LEC for the bulk motion of quasar jets Interplay of the thermal and relativistic plasma outflows from AGN Interplay of the thermal and relativistic plasma outflows from AGN Based on: Gopal Krishna, Dhurde & Wiita (ApJ, 615, L81, 2004) Gopal Krishna, Wiita & Dhurde (MNRAS, 2006, in press) Gopal Krishna, Wiita & Joshi, (Submitted, 2006)

Early Evidence for LEC in the Nuclear Cores Lack of Faraday depolarization (from VLBI)  gmin ~ 100 (Wardle 1977; Jones & O'Dell 1977) (Wardle 1977; Jones & O'Dell 1977) More direct recent evidence for LEC More direct recent evidence for LEC From turnover in the radio spectrum of the eastern hotspot of Cygnus A (nt ~ 0.1 GHz  gmin~300) (nt ~ 0.1 GHz  gmin~300) (Joseph et al 2006; Biermann et al. 1995; Carilli et al. 1991) (Joseph et al 2006; Biermann et al. 1995; Carilli et al. 1991) Near the theoretical estimate for hadronic interactions (gmin ~ 100) Spectral turnover due to LEC can be more readily seen for superluminal VLBI radio knots (Because nt is pushed to GHz range due to strong Doppler shift) (Gopal-Krishna, Biermann & Wiita 2004) (Gopal-Krishna, Biermann & Wiita 2004) For a wide range of B and , LEC is the main cause of spectral flattening/ turnover (Since LEC becomes effective at higher frequency than SSA) (Gopal-Krishna, Biermann & Wiita 2004) (Gopal-Krishna, Biermann & Wiita 2004)

Bulk Lorenz factor of the jet (  j ) from the inverted spectrum of the Extreme Intra-day Variable (IDV) Blazar PKS  =1/3 up to n t  230 GHz  =1/3 up to n t  230 GHz (Protheroe, 2003) Ref: Duschl & Lesch, 1994 Ref: Protheroe, 2003

Other Indications of Ultra-High  j on Parsec / Sub-Parsec Scale To avoid excessive photo-photon losses, variable TeV emission demands Ultra-relativistic jets (Krawczynski et al. 2002) To avoid excessive photo-photon losses, variable TeV emission demands Ultra-relativistic jets (Krawczynski et al. 2002) with 15 <  j < 100 with 15 <  j < 100 (Mastichiadis & Kirk, 1997; Krawczynski, et al. 2001) Correcting the spectrum for Gamma-ray absorption by the IR background strongly implies  j > 50 Correcting the spectrum for Gamma-ray absorption by the IR background strongly implies  j > 50 (e.g., Henri & Saugé, 2006) Evidence for T b (apparent) > K in IDV blazars would also suggest  j > 50 (for simple quasi-spherical geometry of the source) Evidence for T b (apparent) > K in IDV blazars would also suggest  j > 50 (for simple quasi-spherical geometry of the source) (e.g., Protheroe, 2003; Macquart & de Bruyn, 2005) For several EGRET blazars, recent VLBI shows: v app > 25c (hence  j > 25) (Piner et al. 2006) For several EGRET blazars, recent VLBI shows: v app > 25c (hence  j > 25) (Piner et al. 2006) GRB models usually require jets with  j ~ GRB models usually require jets with  j ~ (e.g., Sari et al., 1999; Meszaros, 2002) Note: Jet formation model (  j >30) by Vlahakis & Konigl, 2004)

Problem Posed by Ultra-High  j (> 30) As many as 35% - 50% of the VLBI knots in TeV blazars are found to be stationery or moving subluminally. As many as 35% - 50% of the VLBI knots in TeV blazars are found to be stationery or moving subluminally. (Piner & Edwards 2004) The fraction is much lower for a normal blazar population The fraction is much lower for a normal blazar population (e.g., Jorstad & Marscher, 2003) (Hence, no serious inconsistency with  j ~20-30) (Hence, no serious inconsistency with  j ~20-30) However, a serious inconsistency for TeV blazars

How to Reconcile Ultra-Relativistic Jets with the Slow Moving Radio Knots? Viewing angle (  ) of the jet is within ~ 1 o (from our line of sight) Viewing angle (  ) of the jet is within ~ 1 o (from our line of sight) (NOT a general explanation: Since only ¼  j 2 (~10 -4 ) VLBI knots can appear subluminal) (NOT a general explanation: Since only ¼  j 2 (~10 -4 ) VLBI knots can appear subluminal) Motion of the knots reflects pattern speed, not physical speed (However, see Homan et al. 2006) Motion of the knots reflects pattern speed, not physical speed (However, see Homan et al. 2006) A dramatic deceleration of jet between sub-pc and parsec scale A dramatic deceleration of jet between sub-pc and parsec scale (Georganopoulos & Kazanas, 2003) (Georganopoulos & Kazanas, 2003)DIFFICULTIES Why deceleration in TeV blazars only (and not in EGRET blazars)? Why deceleration in TeV blazars only (and not in EGRET blazars)? Evidence, in fact, points to acceleration on parsec scale (Piner 2006) Evidence, in fact, points to acceleration on parsec scale (Piner 2006) Spine-sheath structure of jets: (e.g., Ghisellini et al. 2004) Spine-sheath structure of jets: (e.g., Ghisellini et al. 2004) Fast spine produces TeV variability via IC and only the slower outer layer is picked in radio VLBI (observational evidence: Giroletti et al2004) DIFFICULTIES Why a two-component jet needs to be invoked only for TeV blazars? Why a two-component jet needs to be invoked only for TeV blazars? Why don't the shocks produce radio knots even in the fast spine? Why don't the shocks produce radio knots even in the fast spine?

Possible resolution of the Paradox: Conical (Ultra-Relativistic) Jets Substantial opening angles are seen for some well-resolved VLBI jets. Substantial opening angles are seen for some well-resolved VLBI jets. Good example of conical VLBI jet is M87 (  >10 o ) Good example of conical VLBI jet is M87 (  >10 o ) (Junor et al., 1999) Consequence of conical jet: For an ultra-relativistic jet, a huge variation of  j (i.e., of Doppler boosting factor & apparent motion) would occur across the jet’s cross section Consequence of conical jet: For an ultra-relativistic jet, a huge variation of  j (i.e., of Doppler boosting factor & apparent motion) would occur across the jet’s cross section Needed: Weighted averaging of  app by the distribution of flux- boosting A(  ) over the jet's cross section Needed: Weighted averaging of  app by the distribution of flux- boosting A(  ) over the jet's cross section (Gopal Krishna et al, 2004) Remember that while A(  ) varies monotonically with ,  app (  ) does not. Remember that while A(  ) varies monotonically with ,  app (  ) does not. Moreover, if the line-of-sight to the core passes through the jet’s cone, then large vector cancellation of  app can occur over the jet’s cross section. Moreover, if the line-of-sight to the core passes through the jet’s cone, then large vector cancellation of  app can occur over the jet’s cross section.

Pseudo-colour rendition of the nucleus of M87 at 43 GHz on 3 March (Junor et al, 1999)

Relevant analytical expressions (Gopal Krishna et al. 2004) S obs =    n (  ).S em (  )d   A(  )S em [where, n=3 for radio knots and A(  )=mean amplification factor] (Fomalont et al. 1991)

Conical Jets w/ High Lorentz Factors Weighted  app vs  for  = 100, 50, 10 and opening angle = 0,1,5 and 10 degrees, With blob  3 boosting Probability of large  app can be quite low for high  if opening angle is a few degrees

High Gammas Yet Low Betas  app vs  for jet and  app vs  for jet and prob of  app >  for opening angles = 0, 1, 5, 10 degrees and  = 50, 10 (continuum  2 boosting) prob of  app >  for opening angles = 0, 1, 5, 10 degrees and  = 50, 10 (continuum  2 boosting) Despite high  in an effective spine population statistics are OK Despite high  in an effective spine population statistics are OK Predict transversely resolved jets show different  app Predict transversely resolved jets show different  app

Some key Implications Thus, even a radio knot moving with the ultra-relativistic spine of the jet would frequently appear to move subluminally (we believe this is the case of TeV blazars). Thus, even a radio knot moving with the ultra-relativistic spine of the jet would frequently appear to move subluminally (we believe this is the case of TeV blazars). This will happen even for viewing angles (  ) significantly larger than 1/  j (Hence, not so unlikely) This will happen even for viewing angles (  ) significantly larger than 1/  j (Hence, not so unlikely) Effective beaming angle is the same as the jet’s opening angle  (5º to 10º) ( >> 1/  j ). Effective beaming angle is the same as the jet’s opening angle  (5º to 10º) ( >> 1/  j ). Usually, this is associated with canonical jets (  =0) of  j =5 to 10. Usually, this is associated with canonical jets (  =0) of  j =5 to 10. Hence, ultra-relativistic conical jets are also consistent with FR I radio galaxies being the parent population of BL Lacs. Hence, ultra-relativistic conical jets are also consistent with FR I radio galaxies being the parent population of BL Lacs.

Dynamical interaction between thermal and relativistic outflows from AGN (Evidence from Radio Morphology ) In several RGs, the inner edges of the two radio lobes are sharply truncated In several RGs, the inner edges of the two radio lobes are sharply truncated Thus, strip-like central gaps are seen in the radio bridges Thus, strip-like central gaps are seen in the radio bridges Typical dimensions of central gaps: Width~30 kpc (  0.5 Mpc) Typical dimensions of central gaps: Width~30 kpc (  0.5 Mpc) Inference: The huge strip-like gap seen between the radio lobe pair betrays the presence of a “Superdisk" made of denser material Inference: The huge strip-like gap seen between the radio lobe pair betrays the presence of a “Superdisk" made of denser material (Gopal-Krishna & Wiita 2000; Gopal-Krishna & Nath 2001) Since the sharp edges can only be seen from a favorable viewing angle, superdisk should be a fairly common feature Since the sharp edges can only be seen from a favorable viewing angle, superdisk should be a fairly common feature Previous Interpretations of the Radio Gaps, in general: Back-flowing synchrotron plasma in the radio lobes is blocked by the ISM of the parent galaxy (ISM arising from stellar winds and/or captured disk galaxies) Back-flowing synchrotron plasma in the radio lobes is blocked by the ISM of the parent galaxy (ISM arising from stellar winds and/or captured disk galaxies) Buoyancy led outward squeezing of the lobe plasma by the ISM Buoyancy led outward squeezing of the lobe plasma by the ISM

3C33 4C C192 3C3813C401 Ref: DRAGN Atlas (P. Leahy)

Need for an Alternative Interpretation Radio gaps in some RGs are extremely wide: upto 0.5 Mpc (PKS ) Radio gaps in some RGs are extremely wide: upto 0.5 Mpc (PKS ) Often the parent galaxy is seen at one edge of the radio gap Often the parent galaxy is seen at one edge of the radio gap (In some cases, even outside the gap, i.e., within a lobe): (3C 16, 3C19) (Saripalli et al. 2002) (DRAGN atlas (P.Leahy)

A Plausible mechanism for the radio gaps Dynamical Interaction of the radio lobes with a powerful thermal wind outflowing from the AGN Dynamical Interaction of the radio lobes with a powerful thermal wind outflowing from the AGN (GK, Wiita & Joshi 2006) Emerging Pieces of Evidence: Emerging Pieces of Evidence: Thermal winds (v w >10 3 km/s) and mass outflow of ~1 M  /yr are generic to AGN Thermal winds (v w >10 3 km/s) and mass outflow of ~1 M  /yr are generic to AGN (e.g., Soker & Pizzolato 2005; Brighenti & Mathews 2006) For example, in ADIOS model, accretion energy mostly ends up in a thermal wind For example, in ADIOS model, accretion energy mostly ends up in a thermal wind (Blandford & Begelman 1999) (Blandford & Begelman 1999) Thus, relativistic jet pair and non-relativistic wind outflow seem to co-exist Thus, relativistic jet pair and non-relativistic wind outflow seem to co-exist (e.g., Binney 2004; Gregg et al. 2006) Evidences: Absorption of AGN's continuum, seen in UV and X-ray bands Evidences: Absorption of AGN's continuum, seen in UV and X-ray bands (review by Crenshaw et al. 2003) Wind outflow probably PRECEDES the jet ejection and lasts for  w > ~ 10 8 yrs Wind outflow probably PRECEDES the jet ejection and lasts for  w > ~ 10 8 yrs (e.g., Rawlings 2003; Gregg et al. 2006) Mechanical luminosity of the wind can greatly exceed AGN’s bolometric luminosity Mechanical luminosity of the wind can greatly exceed AGN’s bolometric luminosity (Churazov et al. 2002; Peterson & Fabian 2005) Wind outflow is quasi-spherical, while the jets are well collimated Wind outflow is quasi-spherical, while the jets are well collimated (e.g., Levine & Gnedin 2005)

The Basic Model: Sequence of Events Wind outflow from AGN blows an expanding bubble of metal-rich, hot gas Wind outflow from AGN blows an expanding bubble of metal-rich, hot gas Later, the AGN ejects a pair of narrow jets of relativistic plasma Later, the AGN ejects a pair of narrow jets of relativistic plasma The jets rapidly traverse the wind bubble and often come out of the bubble The jets rapidly traverse the wind bubble and often come out of the bubble From then on, the high-pressure backflow of relativistic plasma in the radio lobes begins to impinge on the wind bubble, from outside From then on, the high-pressure backflow of relativistic plasma in the radio lobes begins to impinge on the wind bubble, from outside This sideways compression of expanding wind bubble by the two radio lobes transform the bubble into a fat pancake, or superdisk This sideways compression of expanding wind bubble by the two radio lobes transform the bubble into a fat pancake, or superdisk AGN's hot wind escapes through the superdisk region, normal to jets AGN's hot wind escapes through the superdisk region, normal to jets The superdisk is "frozen" in the space. It manifests itself as a strip-like central emission gap in the radio bridge The superdisk is "frozen" in the space. It manifests itself as a strip-like central emission gap in the radio bridge Meanwhile, the galaxy can continue to move within the cosmic web It can move ~ 100 kpc in ~ 300 Myr, with a speed of ~ 300 km/s Meanwhile, the galaxy can continue to move within the cosmic web It can move ~ 100 kpc in ~ 300 Myr, with a speed of ~ 300 km/s Thus, in about 10 8 years the parent galaxy can even reach the edge of the radio emission gap (sometimes, even cross over into the radio lobe: eg., 3C16, 3C19) Thus, in about 10 8 years the parent galaxy can even reach the edge of the radio emission gap (sometimes, even cross over into the radio lobe: eg., 3C16, 3C19) Now onwards, the two jets propagate through very different types of ambient media (wind material and radio lobe plasma) Now onwards, the two jets propagate through very different types of ambient media (wind material and radio lobe plasma)

The Basic Model: Sequence of Events

Modelling the dynamics of the bubble and the jets (Gopal Krishna, Wiita & Joshi 2006) (Uses the analytical works of Levine & Gnedin 2005; Scannapieco & Oh 2004; Kaiser & Alexander 1997) Asymptotic (equilibrium) radius of the wind bubble:

For the jet starting a time t j after the onset of the AGN wind: Catch-up time (t c ): when jet catches up with the bubble’s surface: Catch up length of the jet After catching up [t c >t >(t j +  j )]: Assumption: Jet stops advancing when the AGN switches off.

Gopal Krishna, Wiita & Joshi, 2006

Finding Jet Parameters Determining bulk Lorentz factors, , and misalignment angles, , are difficult for all jets Determining bulk Lorentz factors, , and misalignment angles, , are difficult for all jets Often just set  =1/ , the most probable value Often just set  =1/ , the most probable value Flux variability and brightness temperature give estimates: Flux variability and brightness temperature give estimates:  S = change in flux over time  obs T max = 3x10 10 K  app from VLBI knot speed  is spectral index

Conical Jets Also Imply Inferred Lorentz factors can be well below the actual ones Inferred Lorentz factors can be well below the actual ones Inferred viewing angles can be substantially underestimated, implying deprojected lengths are overestimated Inferred viewing angles can be substantially underestimated, implying deprojected lengths are overestimated Inferred opening angles of < 2 o can also be underestimated Inferred opening angles of < 2 o can also be underestimated IC boosting of AD UV photons by  ~10 jets would yield more soft x-rays than seen (“Sikora bump”) but if  >50 then this gives hard x-ray fluxes consistent with observations IC boosting of AD UV photons by  ~10 jets would yield more soft x-rays than seen (“Sikora bump”) but if  >50 then this gives hard x-ray fluxes consistent with observations So ultrarelativistic jets with  >30 may well be common So ultrarelativistic jets with  >30 may well be common

Inferred Lorentz Factors  inf vs.  for  =100, 50 and 10 for  =5 o P(  ) and

Inferred Projection Angles Inferred angles can be well below the actual viewing angle if the velocity is high and the opening angle even a few degrees Inferred angles can be well below the actual viewing angle if the velocity is high and the opening angle even a few degrees This means that de-projected jet lengths are overestimated This means that de-projected jet lengths are overestimated

Conclusions Part I: Modest opening angles (5º – 10º) of AGN jets can explain the jet Lorenz factor paradox of TeV blazars Part I: Modest opening angles (5º – 10º) of AGN jets can explain the jet Lorenz factor paradox of TeV blazars Thus, the frequently observed subluminal motion of VLBI knots can be reconciled with the ultra-high bulk Lorenz factors (  j >30 – 50) inferred from rapid TeV and radio flux variability. Thus, the frequently observed subluminal motion of VLBI knots can be reconciled with the ultra-high bulk Lorenz factors (  j >30 – 50) inferred from rapid TeV and radio flux variability. Some further consequences of this picture are discussed in our second paper (Gopal Krishna, Wiita & Durde, MNRAS, 2006, in press.) Some further consequences of this picture are discussed in our second paper (Gopal Krishna, Wiita & Durde, MNRAS, 2006, in press.) Part II: Dynamical interaction between thermal (wind) and non-thermal (jet) outflows resulting from the AGN activity, gives rise to fat pancake or superdisk shaped regions. Part II: Dynamical interaction between thermal (wind) and non-thermal (jet) outflows resulting from the AGN activity, gives rise to fat pancake or superdisk shaped regions. The metal-rich in which hot wind material filling the superdisk escapes to hundreds of kpc, roughly orthogonal to the radio axis. The metal-rich in which hot wind material filling the superdisk escapes to hundreds of kpc, roughly orthogonal to the radio axis. Superdisks manifest their presence by causing strip-like emission gaps in the middle of radio bridges. Superdisks manifest their presence by causing strip-like emission gaps in the middle of radio bridges.

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