1. UC Berkeley GBT Measurements of the Zeeman Effect in the Eridanus/Orion Region Tim Robishaw Carl Heiles

4. The Orion Molecular Cloud Complex Heiles 1997 Hat Creek 85 ft 9 years of Zeeman data Distance ~535 pc Bower, Sandstrom, Goldston in prep.

5. Starlight Polarization Orientations Breger 1976, Vrba et al. 1988

6. Starlight Polarization Orientations Breger 1976, Vrba et al. 1988

7. The GBT Is a Zeeman Machine! Off-Axis Design Minimizes Blockage Minimizes Sidelobes!!

8. The GBT Is a Zeeman Machine!

10. Verschuur’s Indictment 1993 BAAS 182 1993 BAAS 183 1995 ApJ 451: 624 1995 ApJ 451: 645

11. Verschuur’s Indictment

12. 3 hours

13. The GBT Hat Creek 85 foot 3 hours

18. OH

25. Summary The GBT can be used as a Zeeman detector Apparent HI self-absorption samples the molecular component of the filament LOS B field measured in emission changes sign across axis of filament –Detections consistent with previous HI emission measurements: they were reliable! Field reverses within central half-degree of filament (~ 4.5 pc) Highest resolution data for modeling of helical magnetic field structure