Submillimeter imaging polarimetry of the NGC 7538 region

Imaging polarimetry of the 850 mum continuum emission in the NGC 7538 regio n, obtained with the SCUBA Polarimeter, is presented. The polarization map is interpreted in terms of thermal radiation by magnetically aligned dust g rains. Two prominent cores associated with IRS 1 and IRS 11, IRS 1(SMM), an d IRS 11(SMM), are found in the surface brightness map. Although these core s look similar in surface brightness, their polarization shows striking dif ferences. In IRS 11(SMM), the polarization vectors are extremely well-order ed, and the degrees of polarization are quite high with an average of simil ar to3.9%. In IRS 1(SMM), on the other hand, the directions of polarization vectors are locally disturbed, and the degrees of polarization are much lo wer than those of IRS 11(SMM). These differences suggest that small scale f luctuations of the magnetic field are more prominent in IRS 1(SMM). This ca n be interpreted in terms of the difference in evolutionary stage of the co res. Inside IRS 1(SMM), which seems to be at a later evolutionary stage tha n IRS 11(SMM), substructures such as subclumps or a cluster of infrared sou rces have already formed. Small scale fluctuations in the magnetic field co uld have developed during the formation of these substructures. The distrib ution of magnetic field directions derived from our polarization map agrees well with those of molecular outflows associated with IRS 1(SMM) and IRS 1 1(SMM). Comparisons of energy densities between the magnetic field and the outflows show that the magnetic field probably plays an important role in g uiding the directions of the outflows.