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Polarization in Interferometry Greg Taylor

Polarization in Interferometry Greg Taylor

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Polarization in Interferometry Greg Taylor

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  1. Polarization in InterferometryGreg Taylor What is polarized light? What fun science can be done with polarimetry? How do interferometers measure polarization? How do you calibrate and image in full polarization? Greg Taylor, Synthesis Imaging School, 18 June 2002

  2. Greg Taylor, Synthesis Imaging School, 18 June 2002

  3. What is Polarized Light? • Light is oscillating electric and magnetic fields • Polarization is labeled by the shape of the trace of the tip of the E vector • Each polarization has an orthogonal state • Incoherent light can contain many polarization states Stokes Parameters describe partially polarized light I = RR + LL Q = RL + LR U = i(LR – RL) V = LL - RR For circular feeds Alternate representation: • pol. angle (EVPA)f = 0.5 atan (U/Q) • polarized intensity p = sqrt(Q2 + U2) • fractional linear m = p / I • fractional circular v = |V | / I Greg Taylor, Synthesis Imaging School, 18 June 2002

  4. 3C 31 VLA @ 8.4 GHz E-Vectors Laing (1996) 3 kpc Greg Taylor, Synthesis Imaging School, 18 June 2002

  5. Perley & Carilli (1996) Cygnus A B-Vectors VLA @ 8.5 GHz 10 kpc Greg Taylor, Synthesis Imaging School, 18 June 2002

  6. 1055+018 Attridge et al 1999 VLBA @ 5 GHz Greg Taylor, Synthesis Imaging School, 18 June 2002

  7. Greg Taylor, Synthesis Imaging School, 18 June 2002

  8. R Aquirrii Stellar SiO Masers Boboltz et al 1998 VLBA @ 43 GHz Greg Taylor, Synthesis Imaging School, 18 June 2002

  9. Greg Taylor, Synthesis Imaging School, 18 June 2002

  10. Taylor (1998) 15 12 8 GHz Greg Taylor, Synthesis Imaging School, 18 June 2002

  11. Greg Taylor, Synthesis Imaging School, 18 June 2002

  12. See Review of “Cluster Magnetic Fields” by Carilli & Taylor 2002 (ARA&A) Greg Taylor, Synthesis Imaging School, 18 June 2002

  13. Greg Taylor, Synthesis Imaging School, 18 June 2002

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  15. Parallactic Angle Greg Taylor, Synthesis Imaging School, 18 June 2002

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  17. Greg Taylor, Synthesis Imaging School, 18 June 2002

  18. Greg Taylor, Synthesis Imaging School, 18 June 2002

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  20. Greg Taylor, Synthesis Imaging School, 18 June 2002

  21. Greg Taylor, Synthesis Imaging School, 18 June 2002

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  25. Bad D-term solution Good D-term solution Greg Taylor, Synthesis Imaging School, 18 June 2002

  26. Greg Taylor, Synthesis Imaging School, 18 June 2002

  27. Compact Symmetric Objects (CSOs) VLBA @ 8.4 GHz Peck & Taylor (2001) Greg Taylor, Synthesis Imaging School, 18 June 2002

  28. Greg Taylor, Synthesis Imaging School, 18 June 2002

  29. Practical VLBI polarization angle calibration Greg Taylor, Synthesis Imaging School, 18 June 2002

  30. 1) Find a Calibrator Greg Taylor, Synthesis Imaging School, 18 June 2002

  31. 2) Estimate f_VLA Greg Taylor, Synthesis Imaging School, 18 June 2002

  32. 2200+420 3) Sum Q and U over VLBA image. 4) Compute f_VLBA = 0.5 atan (U/Q) 5) Rotate VLBA data by (f_VLA – f_VLBA) Greg Taylor, Synthesis Imaging School, 18 June 2002

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  38. Greg Taylor, Synthesis Imaging School, 18 June 2002

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  41. Greg Taylor, Synthesis Imaging School, 18 June 2002