Active Galactic Nuclei: Active Galactic Nuclei: Jets and other OutflowsJets and other Outflows

To discuss two aspects of AGN Activity To discuss two aspects of AGN Activity (About phenomena on parsec & kpc Scales) (About phenomena on parsec & kpc Scales)

Gopal KrishnaGopal KrishnaNCRA-TIFR, Pune, NCRA-TIFR, Pune, INDIAINDIA

Paul J. WiitaPaul J. WiitaGSU, Atlanta, USAGSU, Atlanta, USA

KASI-APCTP Joint Workshop (KAW4), Daejeon, Korea (May 17-19, 2006)

Three topicsThree topics Peculiar radio (synchrotron) spectrum:Peculiar radio (synchrotron) spectrum: SS 1/31/3

Electron energy spectrum: either mono-energetic, orElectron energy spectrum: either mono-energetic, orhaving a low energy cut-off having a low energy cut-off (LEC)(LEC)Salient examplesSalient examples : :

GalacticGalactic (Sgr A* and the "ARC") (Sgr A* and the "ARC") ExtragalacticExtragalactic (extreme IDV quasar PKS 0405-385) (extreme IDV quasar PKS 0405-385)

Possible implication of LEC for the bulk motion Possible implication of LEC for the bulk motion of quasar jetsof quasar jets

Interplay of the thermal and relativistic plasma Interplay of the thermal and relativistic plasma outflows from AGNoutflows 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 CoresEarly Evidence for LEC in the Nuclear Cores

Lack of Faraday depolarization (from VLBI) Lack of Faraday depolarization (from VLBI) gmin ~ 100gmin ~ 100 (Wardle 1977; Jones & O'Dell 1977)(Wardle 1977; Jones & O'Dell 1977)

More direct recent evidence for LECMore direct recent evidence for LEC

From turnover in the radio spectrum of the eastern hotspot of Cygnus From turnover in the radio spectrum of the eastern hotspot of Cygnus AA (nt ~ 0.1 GHz (nt ~ 0.1 GHz gmin~300) 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 Near the theoretical estimate for hadronic interactions (gmin ~ 100)(gmin ~ 100)

Spectral turnover due to LEC can be more readily seen for Spectral turnover due to LEC can be more readily seen for superluminal VLBIsuperluminal VLBIradio knots (Because nt is pushed to GHz range due to strong radio knots (Because nt is pushed to GHz range due to strong Doppler shift)Doppler shift)

(Gopal-Krishna, Biermann & Wiita 2004)(Gopal-Krishna, Biermann & Wiita 2004)

For a wide range of For a wide range of B B and and , LEC is the main cause of spectral , LEC is the main cause of spectral flattening/ turnover (Since LEC becomes effective at higher frequency flattening/ turnover (Since LEC becomes effective at higher frequency than SSA)than SSA)

(Gopal-Krishna, Biermann & Wiita 2004)(Gopal-Krishna, Biermann & Wiita 2004)

Bulk Lorenz factor of the jet (Bulk Lorenz factor of the jet (jj) from the inverted ) from the inverted spectrum of the Extreme Intra-day Variable (IDV) Blazar spectrum of the Extreme Intra-day Variable (IDV) Blazar PKS 0405-385PKS 0405-385

up to up to tt 230 GHz 230 GHz (Protheroe, 2003)

zMeV

E

G

BGHzt 11001.0

32

min

40 i.e., 80 jj

Ref: Duschl & Lesch, 1994 Ref: Protheroe, 2003

Other Indications of Ultra-High Other Indications of Ultra-High jj on Parsec / Sub-Parsec Scaleon Parsec / Sub-Parsec Scale

To avoid excessive photo-photon losses, variable TeV To avoid excessive photo-photon losses, variable TeV emission demands Ultra-relativistic jets emission demands Ultra-relativistic jets (Krawczynski et al. (Krawczynski et al. 2002)2002)

with 15 < with 15 < jj < 100 < 100 (Mastichiadis & Kirk, 1997; Krawczynski, et al. 2001)(Mastichiadis & Kirk, 1997; Krawczynski, et al. 2001)

Correcting the spectrum for Gamma-ray absorption by the Correcting the spectrum for Gamma-ray absorption by the IR background strongly implies IR background strongly implies jj > 50 > 50

(e.g., Henri & Saugé, 2006)(e.g., Henri & Saugé, 2006) Evidence for TEvidence for Tbb (apparent)(apparent) > 10 > 101313 K in IDV blazars would K in IDV blazars would

also suggest also suggest jj> 50 (for simple quasi-spherical geometry > 50 (for simple quasi-spherical geometry of the source)of the source)

(e.g., Protheroe, 2003; Macquart & de Bruyn, 2005)(e.g., Protheroe, 2003; Macquart & de Bruyn, 2005) For several EGRET blazars, recent VLBI shows: For several EGRET blazars, recent VLBI shows:

vvappapp > 25c (hence > 25c (hence jj > 25) > 25) (Piner et al. 2006)(Piner et al. 2006)

GRB models usually require jets with GRB models usually require jets with jj ~ 100-1000 ~ 100-1000(e.g., Sari et al., 1999; Meszaros, 2002)(e.g., Sari et al., 1999; Meszaros, 2002)

Note: Jet formation model (Note: Jet formation model (j j >30) by >30) by Vlahakis & Konigl, 2004Vlahakis & Konigl, 2004))

Problem Posed by Ultra-High Problem Posed by Ultra-High jj (> 30) (> 30)

As many as 35% - 50% of the VLBI knots in TeV As many as 35% - 50% of the VLBI knots in TeV blazars are found to be stationery or moving blazars are found to be stationery or moving subluminally. subluminally.

(Piner & Edwards 2004)(Piner & Edwards 2004)

The fraction is much lower for a normal blazar The fraction is much lower for a normal blazar population population

(e.g., Jorstad & Marscher, 2003)(e.g., Jorstad & Marscher, 2003)

(Hence, no serious inconsistency with (Hence, no serious inconsistency with jj ~20-30) ~20-30)

However, a serious inconsistency for TeV However, a serious inconsistency for TeV blazarsblazars

How to Reconcile Ultra-Relativistic Jets How to Reconcile Ultra-Relativistic Jets with the Slow Moving Radio Knots?with the Slow Moving Radio Knots?

Viewing angle (Viewing angle () of the jet is within ~ 1) of the jet is within ~ 1o o (from our line of sight)(from our line of sight)

(NOT a general explanation: Since only ¼ (NOT a general explanation: Since only ¼ jj2 2 (~10(~10-4-4) VLBI knots can ) VLBI knots can

appear subluminal)appear subluminal)

Motion of the knots reflects pattern speed, not physical speed Motion of the knots reflects pattern speed, not physical speed (However, see (However, see Homan et al. 2006Homan et al. 2006))

A dramatic deceleration of jet between sub-pc and parsec scaleA dramatic deceleration of jet between sub-pc and parsec scale

(Georganopoulos & Kazanas, 2003)(Georganopoulos & Kazanas, 2003)

DIFFICULTIESDIFFICULTIES 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 scaleEvidence, in fact, points to acceleration on parsec scale (Piner 2006)(Piner 2006) Spine-sheath structure of jets:Spine-sheath structure of jets: (e.g., Ghisellini et al. 2004)(e.g., Ghisellini et al. 2004)

Fast spine produces TeV variability via IC and Fast spine produces TeV variability via IC and onlyonly the slower outer the slower outer layer is picked inlayer is picked in radio VLBIradio VLBI (observational evidence:(observational evidence: Giroletti et al2004 Giroletti et al2004) )

DIFFICULTIESDIFFICULTIES 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:Possible resolution of the Paradox: Conical (Ultra-Relativistic) JetsConical (Ultra-Relativistic) Jets

Substantial opening angles are seen for some well-Substantial opening angles are seen for some well-resolved VLBI jets.resolved VLBI jets.

Good example of conical VLBI jet is M87 (Good example of conical VLBI jet is M87 (>10>10oo))(Junor et al., 1999)(Junor et al., 1999)

Consequence of conical jet:Consequence of conical jet: For an ultra-relativistic jet, For an ultra-relativistic jet, a huge variation of a huge variation of jj (i.e., of Doppler boosting factor & (i.e., of Doppler boosting factor & apparent motion) would occur across the jet’s cross apparent motion) would occur across the jet’s cross sectionsection

Needed:Needed: Weighted averaging of Weighted averaging of appapp by the distribution by the distribution of flux-boosting A(of flux-boosting A() over the jet's cross section ) over the jet's cross section

(Gopal Krishna et al, 2004)(Gopal Krishna et al, 2004) Remember that while A(Remember that while A() varies monotonically with ) varies monotonically with , ,

appapp(() does not. ) does not. Moreover, if the line-of-sight to the core passes through Moreover, if the line-of-sight to the core passes through

the jet’s cone, then large vector cancellation of the jet’s cone, then large vector cancellation of appapp can can occur over the jet’s cross section. occur over the jet’s cross section.

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

Relevant analytical expressionsRelevant analytical expressions (Gopal Krishna et al. 2004)(Gopal Krishna et al. 2004)

SSobsobs== n n (()).S.Semem(())dd A A(())SSemem

[where, n=3 for radio knots and A([where, n=3 for radio knots and A()=mean amplification )=mean amplification factor]factor]

ddSS em

n

obsapp

1

5.1 counts; source integral where

sin

:angle viewingofy Probabilit

qdSSdSSN

dAdp

emq

ememem

q

(Fomalont et al. 1991)

Conical Jets w/ High Lorentz FactorsConical Jets w/ High Lorentz Factors

Weighted Weighted app app vs vs for for = 100, 50, 10 and= 100, 50, 10 andopening angle = opening angle = 0,1,5 and 10 degrees,0,1,5 and 10 degrees,With blob With blob 33 boosting boosting

Probability of large Probability of large

appapp can be quite low can be quite low forfor

high high if opening angle if opening angleis a few degreesis a few degrees

High Gammas Yet Low BetasHigh Gammas Yet Low Betas

appapp vs vs for jet and for jet and prob of prob of app app > > for for

opening angles = opening angles = 0, 1, 5, 10 degrees 0, 1, 5, 10 degrees and and = 50, 10 = 50, 10 (continuum (continuum 2 2

boosting)boosting)

Despite high Despite high in in an effective spine an effective spine population population statistics are OKstatistics are OK

Predict Predict transversely transversely resolved jets show resolved jets show different different appapp

Some key ImplicationsSome key Implications

Thus, even a radio knot moving with the ultra-Thus, even a radio knot moving with the ultra-relativistic spine of the jet would frequently relativistic spine of the jet would frequently appear to move subluminally appear to move subluminally (we believe this is the case of TeV blazars).(we believe this is the case of TeV blazars).

This will happen even for viewing angles (This will happen even for viewing angles () ) significantly larger than 1/significantly larger than 1/j j (Hence, not so (Hence, not so unlikely)unlikely)

Effective beaming angle is the same as the jet’s Effective beaming angle is the same as the jet’s opening angle opening angle (5º to 10º) ( >> 1/(5º to 10º) ( >> 1/jj). ).

Usually, tUsually, this is associated with canonical jets his is associated with canonical jets ((=0) of =0) of jj=5 to 10. =5 to 10.

Hence, ultra-relativistic conical jets are also Hence, ultra-relativistic conical jets are also

consistent with FR I radio galaxies being the consistent with FR I radio galaxies being the parent population of BL Lacs.parent population of BL Lacs.

Dynamical interaction between thermal Dynamical interaction between thermal and relativistic outflows from AGNand relativistic outflows from AGN(Evidence from Radio Morphology(Evidence from Radio Morphology))

In several RGs, the inner edges of the two radio lobes are sharply In several RGs, the inner edges of the two radio lobes are sharply truncatedtruncated

Thus, Thus, strip-like central gapsstrip-like central gaps are seen in the radio bridges are seen in the radio bridges Typical dimensions of central gaps:Typical dimensions of central gaps: Width~30 kpc ( Width~30 kpc (0.5 0.5

Mpc)Mpc)

Inference:Inference: The huge strip-like gap seen between the radio lobe The huge strip-like gap seen between the radio lobe pair betrays the presence of a pair betrays the presence of a “Superdisk"“Superdisk" made of denser made of denser materialmaterial

(Gopal-Krishna & Wiita 2000; Gopal-Krishna & Nath 2001)(Gopal-Krishna & Wiita 2000; Gopal-Krishna & Nath 2001)

Since the sharp edges can only be seen from a favorable Since the sharp edges can only be seen from a favorable viewing angle, superdisk should be a fairly common viewing angle, superdisk should be a fairly common featurefeature

Previous Interpretations of the Radio Gaps, in general:Previous Interpretations of the Radio Gaps, in general: Back-flowing synchrotron plasma in the radio lobes is blocked by Back-flowing synchrotron plasma in the radio lobes is blocked by

the ISM of the parent galaxy the ISM of the parent galaxy (ISM arising from stellar winds and/or captured disk galaxies)(ISM arising from stellar winds and/or captured disk galaxies)

Buoyancy led Buoyancy led outward outward squeezing of the lobe plasma by the ISMsqueezing of the lobe plasma by the ISM

3C334C14.27

3C192

3C381 3C401

Ref: DRAGN Atlas (P. Leahy)

Need for an Alternative InterpretationNeed for an Alternative Interpretation

Radio gaps in some RGs Radio gaps in some RGs are extremely wide: are extremely wide: upto 0.5 Mpc (PKS 0114-upto 0.5 Mpc (PKS 0114-476)476)

Often the parent galaxy Often the parent galaxy is seen at one edge of is seen at one edge of the radio gapthe radio gap

(In some cases, even outside the(In some cases, even outside thegap, i.e., within a lobe): gap, i.e., within a lobe): (3C 16, 3C19)(3C 16, 3C19) (Saripalli et

al. 2002)

(DRAGN atlas (P.Leahy)

A Plausible mechanism for the radio gapsA Plausible mechanism for the radio gaps Dynamical Interaction of the radio lobes with a powerful thermal wind Dynamical Interaction of the radio lobes with a powerful thermal wind

outflowing from the AGN outflowing from the AGN (GK, Wiita & Joshi 2006)(GK, Wiita & Joshi 2006)

Emerging Pieces of Evidence:Emerging Pieces of Evidence: Thermal winds (vThermal winds (vww>10>1033 km/s) and mass outflow of ~1 M km/s) and mass outflow of ~1 M/yr are generic to AGN/yr are generic to AGN

(e.g., Soker & Pizzolato 2005; Brighenti & Mathews 2006)(e.g., Soker & Pizzolato 2005; Brighenti & Mathews 2006) For example, in ADIOS model, accretion energy mostly ends up in a thermal windFor 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-existThus, relativistic jet pair and non-relativistic wind outflow seem to co-exist

(e.g., Binney 2004; Gregg et al. 2006)(e.g., Binney 2004; Gregg et al. 2006)

Evidences: Evidences: Absorption of AGN's continuum, seen in UV and X-ray bandsAbsorption of AGN's continuum, seen in UV and X-ray bands(review by Crenshaw et al. 2003)(review by Crenshaw et al. 2003)

Wind outflow probably PRECEDES the jet ejection and lasts for Wind outflow probably PRECEDES the jet ejection and lasts for ww > ~ 10 > ~ 1088 yrs yrs(e.g., Rawlings 2003; Gregg et al. 2006)(e.g., Rawlings 2003; Gregg et al. 2006)

Mechanical luminosity of the wind can greatly exceed AGN’s bolometric luminosityMechanical luminosity of the wind can greatly exceed AGN’s bolometric luminosity(Churazov et al. 2002; Peterson & Fabian 2005)(Churazov et al. 2002; Peterson & Fabian 2005)

Wind outflow is quasi-spherical, while the jets are well collimatedWind outflow is quasi-spherical, while the jets are well collimated(e.g., Levine & Gnedin 2005)(e.g., Levine & Gnedin 2005)

The Basic Model: Sequence of EventsThe Basic Model: Sequence of Events Wind outflow from AGN blows an expanding bubble of metal-rich, hot gasWind outflow from AGN blows an expanding bubble of metal-rich, hot gas

Later, the AGN ejects a pair of narrow jets of relativistic plasmaLater, 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 From then on, the high-pressure backflow of relativistic plasma in the radio lobes begins to impinge on the wind bubble, from outsideradio lobes begins to impinge on the wind bubble, from outside

This sideways compression of expanding wind bubble by the two radio This sideways compression of expanding wind bubble by the two radio lobes transform the bubble into a lobes transform the bubble into a fat pancake, or superdiskfat pancake, or superdisk

AGN's hot wind escapes through the superdisk region, normal to jetsAGN'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 The superdisk is "frozen" in the space. It manifests itself as a strip-like central emission gap in the radio bridgecentral emission gap in the radio bridge

Meanwhile, the galaxy can continue to move within the cosmic web 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/sIt can move ~ 100 kpc in ~ 300 Myr, with a speed of ~ 300 km/s

Thus, in about 10Thus, in about 1088 years the parent galaxy can even reach the edge of years the parent galaxy can even reach the edge of the radio emission gap (sometimes, even cross over into the radio the radio emission gap (sometimes, even cross over into the radio lobe: eg., 3C16, 3C19)lobe: eg., 3C16, 3C19)

Now onwards, the two jets propagate through very different types of Now onwards, the two jets propagate through very different types of ambient media (wind material and radio lobe plasma)ambient media (wind material and radio lobe plasma)

The Basic Model: Sequence of EventsThe Basic Model: Sequence of Events

Modelling the dynamics of the bubble and the jetsModelling the dynamics of the bubble and the jets(Gopal Krishna, Wiita & Joshi 2006)(Gopal Krishna, Wiita & Joshi 2006)

(Uses the analytical works of (Uses the analytical works of Levine & Gnedin 2005; Levine & Gnedin 2005; Scannapieco & Scannapieco & Oh 2004; Kaiser & Alexander 1997) Oh 2004; Kaiser & Alexander 1997)

Asymptotic (equilibrium) radius of the wind bubble:

2

2

12

337

31

605

.10

102.3

1103 where,1

104

3103)(

cmdynG

BP

cmznkTnP

erg

E

PMpcR

lobe

bIGMbmIGM

w

exteq

011;2.1: At 3535

1

IGMmIGMIGM

wbubw zt

LRt

52

53

51

51

6011

107.1:At Gyrm

wbubw tz

erg

EMpcRt

1

860

2

4272

1010/10/1062

yrerg

E

skm

vsgmvLM WWW

WWW

For the jet starting a time tj after the onset of the AGN wind:

bubble within the6.1 51

51

53

jbjjj tLtttR

Catch-up time (tc): when jet catches up with the bubble’s surface:

ccbubcj RtRtR Catch up length of the jet

After catching up [tc>t >(tj+j)]: 5

1

53

6.1

z

LttRtR

IGM

jccj

Assumption: Jet stops advancing when the AGN switches off.

Gopal Krishna, Wiita & Joshi, 2006

Finding Jet ParametersFinding Jet Parameters

Determining bulk Lorentz factors, Determining bulk Lorentz factors, , and misalignment , and misalignment angles, angles, , are difficult for all jets, are difficult for all jets

Often just set Often just set =1/ =1/ , the most probable value, the most probable value Flux variability and brightness temperature give Flux variability and brightness temperature give

estimates:estimates:

TB ,obs S

( obs)2

min TB ,obs

Tmax

1/(3 )

2

app 2min 1

2min

tan 2app

2app 2

min 1

S = change in flux over time obs

Tmax= 3x1010K app from VLBI knot speed is spectral index

Conical Jets Also ImplyConical Jets Also Imply

Inferred Lorentz factors can be well below the Inferred Lorentz factors can be well below the actual onesactual ones

Inferred viewing angles can be substantially Inferred viewing angles can be substantially underestimated, implying deprojected lengths are underestimated, implying deprojected lengths are overestimatedoverestimated

Inferred opening angles of < 2Inferred opening angles of < 2oo can also be can also be underestimatedunderestimated

IC boosting of AD UV photons by IC boosting of AD UV photons by ~10 jets would ~10 jets would yield more soft x-rays than seen (“Sikora bump”) yield more soft x-rays than seen (“Sikora bump”) but if but if >50 then this gives hard x-ray fluxes >50 then this gives hard x-ray fluxes consistent with observationsconsistent with observations

So ultrarelativistic jets with So ultrarelativistic jets with >30 may well be >30 may well be commoncommon

Inferred Lorentz FactorsInferred Lorentz Factors

inf vs. for =100, 50 and 10 for =5o

P() and < inf>

Inferred Projection AnglesInferred Projection Angles

Inferred angles can be well below the actual Inferred angles can be well below the actual viewing angle if the velocity is high and the viewing angle if the velocity is high and the opening angle even a few degreesopening angle even a few degrees

This means that de-projected jet lengths are This means that de-projected jet lengths are overestimatedoverestimated

ConclusionsConclusions Part I:Part I: Modest opening angles (5º – 10º) of AGN jets can Modest opening angles (5º – 10º) of AGN jets can

explain the jet Lorenz factor paradox of TeV blazarsexplain the jet Lorenz factor paradox of TeV blazars Thus, the frequently observed subluminal motion of VLBI Thus, the frequently observed subluminal motion of VLBI

knots can be reconciled with the ultra-high bulk Lorenz factors knots can be reconciled with the ultra-high bulk Lorenz factors ( (j j >30 – 50) inferred from rapid TeV and radio flux variability>30 – 50) inferred from rapid TeV and radio flux variability. .

Some further consequences of this picture are discussed in Some further consequences of this picture are discussed in our second paperour second paper ((Gopal Krishna, Wiita & Durde, MNRAS, 2006, Gopal Krishna, Wiita & Durde, MNRAS, 2006, in press.)in press.)

Part II:Part II: Dynamical interaction between thermal (wind) Dynamical interaction between thermal (wind) and non-thermal (jet) outflows resulting from the AGN and non-thermal (jet) outflows resulting from the AGN activity, gives rise to activity, gives rise to fat pancake fat pancake or or superdisk superdisk shaped shaped regions. regions.

The metal-rich in which hot wind material filling the superdisk The metal-rich in which hot wind material filling the superdisk escapes to hundreds of kpc, roughly orthogonal to the radio escapes to hundreds of kpc, roughly orthogonal to the radio axisaxis..

Superdisks manifest their presence by causing strip-like Superdisks manifest their presence by causing strip-like emission gaps in the middle of radio bridgesemission gaps in the middle of radio bridges. .

Thank youThank you