Magnetic fields in cometary globules. I. CG 22

Abstract

We report first results from a program to study magnetic fields in cometary globules (CGs). These are clouds near massive stars showing a head-tail morphology. Linear optical polarization measurements on stars seen projected on CG 22 in the Gum- Vela region presented. A majority of the stars seen within the Boundary of the cloud show a polarization of ~ 1 per cent with the electric field vector oriented parallel to the tail, whereas those outside the boundary either show small polarization with position angels parallel to the galactic plane or show no polarization within the errors of our measurements. If the polarization is due to dust grains aligned by magnetic fields, our results imply that the fields in CG 22 is parallel to its tail. A rough estimate of the field strength (~ 30 μG) indicates that it may be important for the dynamics of the cloud. These results support the idea that magnetic fields play a role in producing the structures seen in the tails of the CGs. We suggest that the alignment of the magnetic field could only have been caused by the same process that shaped the tails. We also comment on the implications of the polarization detected in the light from the star Wra 220, a T Tauri star believed to have formed in the head of CG 22.