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Polarization 101

Polarization 101. Absorption. Emission. Scattering. Polarization of Background Starlight. Polarization of Thermal Radiation. Polarization of Scattered Starlight. WARNING: This illustration is for single scattering, and a single source of illumination. “fake” stars (scattered

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Polarization 101

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  1. Polarization 101 Absorption Emission Scattering

  2. Polarization of Background Starlight

  3. Polarization of Thermal Radiation

  4. Polarization of Scattered Starlight WARNING: This illustration is for single scattering, and a single source of illumination.

  5. “fake” stars (scattered light peaks only) “real” star (center of scattered-light polarization pattern) Will the true source please stand up? AFGL 2146 “The Juggler” Note: This kind of map also gives disk orientation and information on outflow cavity. Minchin et al. 1991 Circumstellar Nebulae

  6. "Cores" and Outflows Large Molecular Clouds Jets and Disks Solar System Formation What’s good where (now)? Background Starlight but not inside cold, dark clouds Thermal Emission nothing yet... Thermal Emission & Scattered Light

  7. The Galaxy Serkowski, Mathewson & Ford, et al. Magnetic Fields

  8. Naïveté:The waywe once thoughtthings might be... Magnetic Fields

  9. B216-217 Dark Cloud Complexes: 1-10 pc scales Magnetic Fields

  10. Galaxy (Jones, Klebe & Dickey 1992) B216-217 (Goodman et al. 1992) Fit to these dark clouds L1755 (Goodman et al. 1995) Cold Dark Clouds: (Not) Looking Inside 3 2 Polarization [%] 1 0 0 2 4 6 8 10 Extinction [mag] Magnetic Fields

  11. Dark Cloud Complexes: 1-10 pc scales Magnetic Fields

  12. 0 1 2 3 4 3.0 2.5 2.0 [%] R P 1.5 1.0 0.5 0.0 0 1 2 3 4 A [mag] V Background to Cold Dark Cloud Background to General ISM “Go no further than AV~1.3 mag.” Arce et al. 1998 Magnetic Fields

  13. Dark Cloud Complexes: 1-10 pc scales3D MHD simulation of Gammie, Stone & Ostriker (in prep.) Field lines “look” straight-ish, even though B is significant. Magnetic Fields

  14. Wavelength [cm] far-IR: KAO SOFIA M3/Balloon 100 10 1 0.1 0.01 0.001 -8 10 Emissivity-Weighted, normalized, blackbodies -10 10 ] -1 -12 sub-mm: JCMT, CSO SMA 10 ster -1 Hz -14 10 -2 cm -1 -16 10 [erg sec mm: OVRO, BIMA MMA n B -18 10 100 K 30 K -20 10 10 K 8 9 10 11 12 13 14 10 10 10 10 10 10 10 Frequency [Hz] Thermal Emission Polarimetry Magnetic Fields

  15. B? B? B? Right Ascension (1950) Polarization of Background Starlight in M17 Schulz et al. 1981 Polarization of 100 mm Emission in M17 Dotson 1995 M17 4% Right Ascension (1950)

  16. Thermal Emission Polarimetry around Individual YSO’s & Outflows 1000 A.U. 3-mm OVRO -- Akeson et al. 1996 Magnetic Fields

  17. 6000 A.U. Outflow along the B-field? (Yes, maybe.) B What about the large scale field? CO outflow -- Blake et al. 1995 Magnetic Fields

  18. Relation to the Large-Scale field Goodman et al. 1990 How about the small-scale field? Magnetic Fields

  19. "Cores" and Outflows Large Molecular Clouds Jets and Disks Solar System Formation PPV: What’s good where (then)? Background Starlight & Thermal Emission (SOFIA, balloons, satellites) Thermal Emission (SOFIA & better receivers) Scattered Light (A.O. or big satellite) Thermal Emission (new interferometers) & Scattered Light (adaptive optics)

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