1. Polarization 101 Absorption Emission Scattering

2. PolarizationPolarization of Background Starlight

3. PolarizationPolarization of Thermal Radiation

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

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

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

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

8. Magnetic Fields Naïveté: Naïveté: The way we once thought things might be...

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

10. Magnetic Fields Polarization [%] Cold Dark Clouds: (Not) Looking Inside 3 2 1 0 1086420 Extinction [mag] B216-217 (Goodman et al. 1992) L1755 (Goodman et al. 1995) Galaxy (Jones, Klebe & Dickey 1992) Fit to these dark clouds

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

13. Magnetic Fields “Go no further than A V ~1.3 mag.” 3.0 2.5 2.0 1.5 1.0 0.5 0.0 P R [%] 43210 43210 A V [mag] Background to Cold Dark Cloud Arce et al. 1998 Background to General ISM

14. Magnetic Fields Dark Cloud Complexes: 1-10 pc scales 3D MHD simulation of Gammie, Stone & Ostriker (in prep.) Field lines “look” straight-ish, even though B is significant.

15. Magnetic Fields Thermal Emission Polarimetry 10 -20 10 -18 10 -16 10 -14 10 -12 10 -10 10 -8 B [erg sec cm -2 Hz ster ] 0.0010.010.1110100 Wavelength [cm] 10 8 9 11 10 12 10 13 10 14 Frequency [Hz] Emissivity-Weighted, normalized, blackbodies 10 K30 K 100 K sub-mm: JCMT, CSO SMA far-IR:KAOSOFIAM3/Balloon mm: OVRO, BIMA MMA

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

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

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

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

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