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AGN: Linear and Circular Polarization

AGN: Linear and Circular Polarization. Dan Homan Denison University. AGN Science with Polarization. 3-D magnetic field structure of jets Role in collimation & acceleration of jets Connection with SMBH/Accretion Disk? Low energy particle population Particle acceleration mechanisms

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AGN: Linear and Circular Polarization

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  1. AGN: Linear and Circular Polarization Dan Homan Denison University

  2. AGN Science with Polarization • 3-D magnetic field structure of jets • Role in collimation & acceleration of jets • Connection with SMBH/Accretion Disk? • Low energy particle population • Particle acceleration mechanisms • Particle content & kinetic luminosity of jets • Tracer of jet flow and hydrodynamics • Shock, shear, aberration, etc… • Probe of material + fields external to jets • Sheath or boundary layers • Narrow line region

  3. Rotation Measure Gradients 3C 273 Asada et al. 2002 Multiple Scales and Epochs: Zavala & Taylor 2005; Attridge et al. 2005 with mm VLBI; Asada et al. 2008

  4. MOJAVE Multi-band observations: 8.1, 8.4, 12.1, 15.3 GHz Hovatta et al., in prep.

  5. TeV Blazar: Markarian 501 (Croke et al. 2010) Other Jets: Gabuzda et al. 2004; Asada et al. 2008; Gomez et al. 2008; O’Sullivan & Gabuzda 2009; Mahmud et al. 2009; Asada et al. 2010

  6. Evidence for Helical/Toriodal Fields? • Gradients in Faraday Rotation Across Jets… • Due to Toroidal field structures within jets or in a boundary layer surrounding them? • Could they be due to external pressure gradients? • If Toroidal Fields… • Role in Collimation & Acceleration • Jets carry a current (where is it… how does it flow?)

  7. Jet Structure at 18-22 cm Gabuzda et al. VLBA program

  8. 18-22 cm Study of MOJAVE-I Sample Gabuzda et al. VLBA program Coughlan et al. 2010

  9. 20 pc MOJAVE: Quasar 0333+321 (NRAO 140) z = 1.26 2005-09-23 Apparent Speed = 12.8c (Lister et al. 2009)

  10. 20 pc MOJAVE: Quasar 0333+321 (NRAO 140) z = 1.26 2005-09-23

  11. MOJAVE-I CP Results • Circular Polarization detected (≥ 3 ) in at least one epoch in 54 of 133 jets • Wide variety of variability behavior • No clear correlation between linear and circular polarization • Sign Preference? • 20 jets have multiple epoch ≥ 3  detections Only 1/20 changes sign • 49 jets have multiple epoch ≥ 2  measurements Only 2/49 change sign

  12. 8.0 GHz 3C279 z=0.536 1 mas = 6.3 pc Nov. 2005 24.3 GHz Nov. 2005 VLBA at 6 frequencies from 8.0 GHz to 24.3 GHz

  13. Core Region of 3C279

  14. Polarization Model of Components 5 and 4

  15. Multi-band Radiative Transfer • For Jet components and Jet core in 3C279 (Homan et al. 2009) • Relativistic low energy cutoff: 5 ≤ l ≤ 35 • Strong poloidal magnetic field in core of jet: Estimated flux: 2 x 1034 - 1 x 1035 G cm2 • Jet is dynamically dominated by protons.

  16. Requirements • Polarized Emission at Jet Edges (Gradient, Sheath, Jet-Environment interaction Studies) • 1st: Sensitivity, 2nd (u,v)-coverage (short baselines) • Multi-band Linear and Circular Polarization (Radiative Transfer fitting over factor of 3-4 in frequency) • 1st: (u,v)-coverage (long baselines), 2nd Sensitivity • Linear Polarization of bright jet components (Tracer of jet component motion, shock strength/orientation/aberration) • Sensitivity

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