EVPA SWING MECHANISMS IN AGN JETS:

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1 EVPA SWING MECHANISMS IN AGN JETS: STOCHASTIC VS. DETERMINISTIC by Sebastian Kiehlmann on behalf of the Quasar Movie Project team PI: Dr. Tuomas Savolainen Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, Bonn, Germany

2 Outlook i. Introduction: AGN jets and EVPA swings ii. Random walks in Stokes-Q-U-space iii. EVPA swing mechanisms iv. Helical motion model

3 I. Introduction: AGN Jets Fig. 1: Sketched Active Galactic Nucleus 1

4 I. Introduction: AGN Jets Fig. 1: Sketched Active Galactic Nucleus 1

5 I. Introduction: AGN Jets Fig. 1: Sketched Active Galactic Nucleus 1

6 I. Introduction: AGN Jets Fig. 1: Sketched Active Galactic Nucleus 1

7 I. Introduction: Blazar SED Fig. 2: Sketched spectral energy distributions of a blazar 2

8 I. Introduction: EVPA swings Fig. 3: 3C 279 optical polarization curve 3

I. Introduction: EVPA swings object EVPA rotation time interval explanation reference OJ 287 120 7 d Helical magnetic field Kikuchi et al.

9 I. Introduction: EVPA swings object EVPA rotation time interval explanation reference OJ d Helical magnetic field Kikuchi et al., 1988 BL Lac d Helical magnetic field Marscher et al., 2008 PKS d Helical magnetic field Marscher et al., C d Helical magnetic field Larionov et al., C d Bent jet Abdo et al.,

, 1988 BL Lac 240 5 d Helical magnetic field Marscher et al.

10 II. Random walk: randomized Stokes parameters For each cell i 1, N : q i = U( 1, +1) u i = U( 1, +1) Fig. 5.1 Q i = U i = q i q i 2 + u i 2 u i q i 2 + u i 2 m l,max m l,max m l,max = 75 % T.W. Jones et al. 1985, ApJ F. D Arcangelo et al. 2007, ApJ 5

11 II. Random walk: simple and shock RW process Simple random walk process: Shock random walk process: Fig. 5.2 Fig. 6 6

12 II. Random walk: parameters Cells: N cells m l = m l,max π 4N cells Variation rate: n var d 1 Fig. 7: Random walk processes: expectation value of the polarization fraction variation 7

13 II. Random walk: parameters Vary: N cells Number of cells n var Variation rate Measure: m l Polarization mean σ m l Polarization variation Δχ EVPA swing amplitude s Variation estimator N Shifting consistency 8

mean σ m l Polarization variation Δχ EVPA swing

14 III. Stochastic vs. deterministic: 3C 279 polarization Fig. 8: 3C 279 R-band flux, opt. lin. pol. fraction and EVPA 9

15 IV. EVPA swing mechanisms: Thick-to-thin-transition Optically thick to optically thin transition in radio, not in optical Swing amplitude: Δχ = 90 for details: Ioannis Myserlis presentation 10

16 IV. EVPA swing mechanisms: Two/multi-component model Ref.: Holmes et al. 1984, MNRAS Fig. 4: Two-component polarization curve Swing amplitude: Δχ 90 11

17 IV. EVPA swing mechanisms: Bent trajectory Ref.: Nalewaiko, 2012, IJMPD Fig. 5: Bent trajectory EVPA swing, Nalewaiko, 2012 e.g. bent jet Swing amplitude: Δχ

18 IV. EVPA swing mechanisms: Helical motion Ref.: e.g. Marscher et al., 2008, Nature Fig. 6.1: Sketched jet and B-field geometry, EVPA rotation Helical motion of an emission feature in a helical magnetic field 13

19 V. Helical motion model: parameters Motion and geometric parameters: Acceleration a/c d 1 Begin acceleration zone z ba R S End acceleration zone zea R S Downstream Lorentz factor Γ z,0 Fig. 6.2: Sketched helical motion model geometry Initial angular velocity π 0 /d Initial radial position r 0 R S Initial angular position φ 0 Opening index ρ 1 Opening offset z 0 R S Viewing angle θ Jet angle η Magnetic field parameters: Magn. field pitch angle b Component intrinsic flux density: Intr. flux density intr f ν mjy Spectral index α =

2: Sketched helical motion model geometry Initial angular velocity π 0 /d Initial radial position r 0 R S Initial angular position φ 0

20 V. Helical motion model: Single component 15

V. Helical motion model: parameters Motion and geometric parameters: Acceleration a/c d 1 Begin acceleration zone z ba R S End acceleration zone zea R S Downstream Lorentz factor Γ z,0 Initial

21 V. Helical motion model: parameters Motion and geometric parameters: Acceleration a/c d 1 Begin acceleration zone z ba R S End acceleration zone zea R S Downstream Lorentz factor Γ z,0 Initial angular velocity π 0 /d Angular momentum conservation Relativistic aberration Time dilation: cosmological, motion Initial radial position r 0 R S Initial angular position φ 0 Opening index ρ 1 Opening offset z 0 R S Viewing angle θ Jet angle η Magnetic field parameters: Magn. field pitch angle b Component intrinsic flux density: Intr. flux density intr f ν mjy Spectral index α = 0.7 Polarized background: Background flux density bg f ν mjy Background EVPA χ bg Background polarization P bg % Component polarization P comp % Constants: SMBH mass M SMBH = M Redshift z =

22 V. Helical motion model: Single component + background 17

23 Conclusions Random walks: 3C 279: two EVPA rotation processes Low-state: stochastic variation Flaring state: deterministic variation Helical motion in helical magnetic field model: Can explain two-directional EVPA swings as observed in 3C

24 Special thanks to the QMP collaborators: T. Savolainen (PI), S.G. Jorstad, F. Schinzel, K.V. Sokolovski, I. Agudo, M. Aller, I. Berdnikov, V. Chavushyan, L. Fuhrmann, M. Gurwell, R. Itoh, J. Heidt, Y.Y. Kovalev, T. Krajci, O. Kurtanidze, A. Lähteenmäki, V.M. Larionov, J. León-Tavares, A.P. Marscher, K. Nilson, the AAVSO, the Yale SMARTS project and all the observers. Acknowledgements: SK was supported for this research through a stipend from the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Max Planck Institute for Radio Astronomy in cooperation with the Universities of Bonn and Cologne. Data from the Steward Observatory spectropolarimetric monitoring project were used. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, and NNX12AO93G. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research.

25 Appendix A. nπ-ambiguity: Fig. 1.2: Sketched modified EVPA curve Fig. 1.1: Sketched EVPA curve I

26 Appendix Method 1: A. nπ-ambiguity: Shifting methods Method 2: Fig. 2.1 Fig. 2.2 ΔΧ i = Χ i Χ i 1 Χ ref,i = Χ i 1 N, Χ i 1 σ 2 Χ i + σ 2 Χ i 1 N = 1, 2, 3, if ΔΧ i > 90 if Χ i Χ ref,i > 90 Χ mod,i = Χ i ± n 180 II

27 Appendix A. nπ-ambiguity: Shifting consistency Fig. 3: 3C 279 measured and shifted EVPA III

28 Appendix B. Curve smoothness: Fig. 4: 3C 279 measured, shifted EVPA and pointto-point-variation IV

29 Appendix B. Curve smoothness: Variation estimator ΔΧ Point-to-point variation: Δt Tendency: m = Variation estimator: s = = Χ i Χ i 1 i t i t i 1 ΔΧ Δt i ΔΧ Δt i m V

30 Appendix B. Curve smoothness: Variation estimator s = /d s = 5.7(5) /d s = 5.5(5) /d VI

M87: The Rosetta Stone of AGN Jets

M87: The Rosetta Stone of AGN Jets Image credit: W. B. Sparks (STScI) Masa Nakamura (ASIAA) Collaborators: K. Asada (ASIAA), D. Meier (JPL), D. Garofalo (CSUN), C. Norman (JHU) EHT Meeting@Tucson, Jan.