2001/03/21 by M. Momose, Munetake Momose, Motohide Tamura +8 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/321516
18 pages, 5 figures, accepted by ApJ, PS/PDF version with figures in full resolution is available at http://stars.sci.ibaraki.ac.jp/~momose/publication.html
arxiv created 2001/03/21 · openalex publication_date 2001/07/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Imaging polarimetry of the 850 μm continuum emission in the NGC 7538 region, obtained with the SCUBA Polarimeter, is presented. The polarization map is interpreted in terms of thermal radiation by magnetically aligned dust grains. Two prominent cores associated with IRS 1 and IRS 11, IRS 1(SMM), and IRS 11(SMM), are found in the surface brightness map. Although these cores look similar in surface brightness, their polarization shows striking differences. In IRS 11(SMM), the polarization vectors are extremely well-ordered, and the degrees of polarization are quite high with an average of ~3.9%. In IRS 1(SMM), on the other hand, the directions of polarization vectors are locally disturbed, and the degrees of polarization are much lower than those of IRS 11(SMM). These differences suggest that small scale fluctuations of the magnetic field are more prominent in IRS 1(SMM). This can be interpreted in terms of the difference in evolutionary stage of the cores. Inside IRS 1(SMM), which seems to be at a later evolutionary stage than IRS 11(SMM), substructures such as subclumps or a cluster of infrared sources have already formed. Small scale fluctuations in the magnetic field could have developed during the formation of these substructures. The distribution of magnetic field directions derived from our polarization map agrees well with those of molecular outflows associated with IRS 1(SMM) and IRS 11(SMM). Comparisons of energy densities between the magnetic field and the outflows show that the magnetic field probably plays an important role in guiding the directions of the outflows.