UNDERSTANDING POWERFUL JETS AT DIFFERENT SCALES IN THE FERMI ERA. B. THE KPC SCALE: X-RAY EMISSION MECHANISM AND JET SPEED

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1 UNDERSTANDING POWERFUL JETS AT DIFFERENT SCALES IN THE FERMI ERA. A. THE PC SCALE: LOCATING THE Γ-RAY EMISSION SITE B. THE KPC SCALE: X-RAY EMISSION MECHANISM AND JET SPEED Markos Georganopoulos 1,2 Eileen Meyer 3 Amanda Dotson 1 David Rivas 1 1 University of Maryland, Baltimore County 2 NASA Goddard Space Flight Center 3 Space Telescope Institute

2 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

3 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

4 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

5 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

6 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

7 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

8 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

9 PRESENTATION OVERVIEW A. How far from the central engine is the Fermi emission being produced? 1. The variability argument: inside the sub-pc broad line region (BLR) 2. The pair production argument: outside the BLR 3. The multiwavelength flare monitoring: about 10 pc away. 4. The Fermi flare energy dependence cooling time method. 5. The radiative deceleration method. 1. Synchrotron or Inverse Compton (IC)? 2. 3C 273: Fermi analysis rules out the IC model B. Chandra Kpc scale X-ray emission:

10 THE LOCATION OF THE GEV POWER DISSIPATION: THE VARIABILITY TIMESCALE ARGUMENT Relevant length scales: The broad line region (BLR) R BLR ~ pc The molecular torus (MT) R MT ~ 1-few pc The VLBI radio jet features R VLBI ~10 pc t var ~1-3 hours Assuming that the entire jet cross section participates: R r Tavecchio et al Dt var = r(1+ z), q = r cd R Þ R = Dt varcd q(1+ z)» 0.1 pc Dt var,3hour G 2 1 (1+z) -1 for d = G, q =1/ G This is inside the BLR

11 THE LOCATION OF THE GEV POWER DISSIPATION: THE VARIABILITY TIMESCALE ARGUMENT Nature can produce variations in regions much smaller that the jet cross section: Kpc scale knots of Pictor A vary within a few years (Marshall 2010) Total Localized energy dissipation with r blazar <r jet (e.g. Begelman et al. 2008, Giannios et al. 2009) => We could have fast variability regardless of the distance from the central engine.

12 THE LOCATION OF THE GEV POWER DISSIPATION: THE PAIR PRODUCTION ARGUMENT γ-γ pair production threshold at ε 1 ε 2 =1, From Chris Done s thesis Cross section peak of ~ 0.2 σ T at ε 1 ε 2 =2. BLR Lyα photons: ε 1 ~ Absorption maximized for ε 2 ~10 5 or in the observer s frame E~50/(1+z) GeV, and remains significant up to ~ 1(1+z) TeV The optical depth of propagation through the BLR is t» 0.2 s T n Lya R BLR, n Lya = L Lya 2 4pcR BLR E Lya

13 THE LOCATION OF THE GEV POWER DISSIPATION: THE PAIR PRODUCTION ARGUMENT Optical depths τ~2-10 are expected, but absorption features are not seen in the multi-gev SED: PKS C 279 (Albert et al. 2008) PKS 1222_21 (Aleksic et ak. 2011) (Pacciani et al. 2012) PKS (Abramowski 2013) PKS B (Tavecchio et al. 2013) At least for these sources the γ-rays cannot be produced within the BLR.

14 THE LOCATION OF THE GEV POWER DISSIPATION: THE MULTIWAVELENGTH ARGUMENT Agudo et al. 2010: Multiwavelenth polarimetric observations put the blazar at >14 pc from the central engine. See also Marcher 2008 and a series of publications of the BU group.

15 THE LOCATION OF THE GEV POWER DISSIPATION: THE ENERGY DEPENDENT FERMI VARIABILITY METHOD Dotson et al. 2012: Cooling on the UV BLR photons takes place at the onset of the Klein-Nishina regime for the GeV emitting electrons and it is practically energy independent. BLR Cooling on the IR MT photons takes place in the Thomson regime and it is energy dependent. If the decay time of fast Fermi flares is energy independent the emission takes place in the BLR MT 1. Split the Fermi energy band to low (< MeV) and high energies. 2. Fit to each flare an exponential rise and decay profile: F(t) = 2F 0 (e (t 0-t)/T R +e (t 0+t)/T F ) -1

16 Flux (ph cm^-2 s^-1) 0e+00 1e-05 2e-05 3e-05 Flux (ph cm^-2 s^-1) 0e+00 2e-06 4e-06 6e-06 8e-06 1e-05 THE LOCATION OF THE GEV POWER DISSIPATION: THE ENERGY DEPENDENT FERMI VARIABILITY METHOD In most cases the decay time in high and low energies are statistically the same. Then, the blazar is either inside the BLR or inside a compact MT. E>500 MeV HE Data 3h PKS T f,he =3.7±1.0 h To estimate the maximum distance from the central engine A. Estimate a maximum time difference between the cooling times: DT max = T F,LE -T F,HE + TErr 2 2 F,LE +TErr F,HE 4. Use this to constrain the distance of the emission from the central engine: E<500 MeV Dotson et al in prep. MET (s) LE Data 3h T f,le =2.9±1.1 h R 1.1 pc MET (s)

17 Flux (ph cm^-2 s^-1) 0e+00 1e-06 2e-06 3e-06 Flux (ph cm^-2 s^-1) 0.0e e e e-05 THE LOCATION OF THE GEV POWER DISSIPATION: THE ENERGY DEPENDENT FERMI VARIABILITY METHOD In a couple of cases the decay time is is significantly slower in the low energies, indicating it takes place outside the BLR and inside a MT with a radius of a few pc. PKS again, now flaring inside a MT of radius ~ 7pc HE Data 3h E>500 MeV T f,he =11.1±6.0 h LE Data 3h E<500 MeV T f,he =37.6.±14.0 h MET (s) MET (s)

18 THE LOCATION OF THE GEV POWER DISSIPATION: THE RADIATIVE DECELERATION CASE Motivation: The jet power of powerful jets is L jet ~ erg s -1 The observed luminosity of these systems assuming isotropy is L obs ~10 48 erg s -1 which correspond to a beaming corrected luminosity of L g ~ L obs / G 2 ~ erg s -1 Radiation that is anisotropic in the comoving frame (EC in the MT or BLR, not synchrotron or SSC), carries away momentum and the flow can slow down considerably, since L γ ~L jet. VLBI observations of high superluminal speeds exclude jets that would decelerate significantly in the MT, possibly requiring the blazar emission to take place beyond the MT.

19 THE LOCATION OF THE GEV POWER DISSIPATION: THE RADIATIVE DECELERATION CASE External Compton +relativistic flow Radiative deceleration. How much will the jet decelerate radiatively in the MT? 3 pc For a leptonic jet the characteristic deceleration length is l ~ ( s T mc 2 U MTGg) -1 ~10-2 U -1 MT,-4G -1 1 g -1 4 pc Γ e - e + Γ one p per e - If there is one proton per electron, raising the jet power to values close to Eddington, the deceleration stops when γ drops to γ~m p /m e. Georganopoulos & Rivas, in prep. Already Clear: No leptons only jet in the MT

20 2000: CHANDRA DETECTS THE KCP SCALE JET OF THE SUPERLUMINAL QUASAR PKS projected length~100 Kpc Chartas et al Schwartz et al The X-rays is neither SSC (dashed line), nor EC off the CMB (dotted line) In equipartition and no beaming they underproduce the X-ray flux by !

21 2000: CHANDRA DETECTS THE KCP SCALE JET OF THE SUPERLUMINAL QUASAR PKS projected length~100 Kpc Chartas et al Schwartz et al Apparent superluminal (u>c) velocities (Lovell et al. 2000): Relativistic flow (Γ~15) in pc-scale jet pointing close to the observer. What if the flow remains relativistic at the X-ray knots?

22 2000: CHANDRA DETECTS THE KCP SCALE JET OF THE SUPERLUMINAL QUASAR PKS For a given synchrotron luminosity, beaming decreases the level of SSC luminosity in equipartition

23 2000: CHANDRA DETECTS THE KCP SCALE JET OF THE SUPERLUMINAL QUASAR PKS For a given synchrotron luminosity, beaming increases the level of EC luminosity in equipartition

24 WHAT IS THE X-RAY EMISSION MECHANISM?

25 WHAT IS THE X-RAY EMISSION MECHANISM? Inverse Compton scattering off the CMB (EC/CMB) (Tavecchio et al. 2000, Celotti et al. 2001) Extends the electron energy distribution (EED) down to MeV energies Requires relativistic large scale jets (Γ~10) (super) Eddington jet power requirements, radiatively inefficient (Dermer & Atoyan 2002, 2004)

26 WHAT IS THE X-RAY EMISSION MECHANISM? Synchrotron (e.g. Harris et al. 2004, Hardcastle 2006) Additional EED component at ~1-100 TeV energies No need for highly relativistic large scale jet More economical in jet power, radiatively efficient, but what is the second electron population?

27 PREDICTIONS OF THE EC/CMB MECHANISM FOR THE Γ-RAYS Q: What γray emission is predicted by the EC/CMB model? n c = 2pm ec(1+ z)v 0 n s e(b /d) = (B /d) -1 = d 2 A: The γ-ray SED depends on a single parameter (B/δ) or just δin equipartition. Β/δ (or δ in equipartition) is fixed by the requirement to fit the radio-optical and X- ray SED. L c = 32pU 0 (1+ z)4 = (B /d) -2 = d 4 L s 3(B /d) 2 Georganopoulos et al δ 2 δ 4 The γ-ray SED is determined with no freedom.

28 3C 273 PREDICTIONS OF THE EC/CMB MECHANISM FOR THE Γ-RAYS The γ-ray observed emission is the sum of the variable blazar component and the steady large scale jet emission. 3C 273 was below the EGRET sensitivity limit for more than half of the times it was observed. Uchiyama et al Von Montigny et al 1997 The lowest GeV flux observed is an upper limit for the large scale jet flux.

29 PREDICTIONS OF THE EC/CMB MECHANISM FOR THE Γ-RAYS EGRET limits require δ<11.9, assuming equipartition. Georganopoulos et al. 2006

30 FERMI RULES OUT THE EC/CMB MECHANISM FOR 3C 273 Meyer & G 2013 Obtaining an upper limit for the large scale jet γ-ray emission: Stich together 2-week GTI intervals of low flux and flux upper limits. Patience is rewarded after almost 3 years of high Fermi fluxes.

31 FERMI RULES OUT THE EC/CMB MECHANISM FOR 3C 273 Meyer & G 2013 The EC/CMB modelγ-ray flux for knot A violates the 3-10 GeV flux upper limit at more than the 99.9% level. EC/CMB FOR 3C 273 IS RULED OUT.

32 FERMI RULES OUT THE EC/CMB MECHANISM FOR 3C 273 Meyer & G 2013 To satisfy the 3-10 GeV flux upper limit requires δ<9.

33 FERMI RULES OUT THE EC/CMB MECHANISM FOR 3C 273 Can we constrain δ more? Sum up the flux of many knots The radio polarization direction up to knot D1 is parallel to the jet, then abruptly turns by 90 o, possibly by strong deceleration at a shock. Conway et al The equipartition magnetic field varies by less than a factor of 2 along the A to D1 knots Assumption: A single δ and B characterize all the knots from A to D1. Jester al. 2005

34 FERMI RULES OUT THE EC/CMB MECHANISM FOR 3C 273 SED of the sum of knots A to D1: To satisfy the Fermi upper limit we require δ eq <5.0

35 CONCLUSIONS: With Fermi, we begin to understand how far from the black hole does the jet dissipates radiatively a power as large as black hole s Eddington luminosity. Distributed power disipation at discrete different distances is in agreement with our current understanding. Fermi rules out the Extrenal Compton mechanism for the large scale jet of 3C 273 and constraints δ<~5. The X-rays are synchrotron and come from in situ electron acceleration reaching energies of 100 TeV