Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...286..579m&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 286, no. 2, p. 579-587
Astronomy and Astrophysics
Astrophysics
39
Gas Jets, Interstellar Matter, Molecular Flow, Polarization (Waves), Stellar Envelopes, Stellar Magnetic Fields, Stellar Mass Ejection, Astronomical Polarimetry, Dust, Submillimeter Waves
Scientific paper
We have detected 800 micrometer polarization at the flux peak and positions around the outflow sources DR 21 and NGC 7538-IRS 11. For both sources the direction of the polarization vectors is extremely uniform and the dispersion is small. This implies that, within the resolution of our observations, the magnetic field is both uniform in direction and strong. The direction of the magnetic field around DR 21 does not appear to be aligned with either the direction of the outflow axis or the major axis of the submm circumstellar dust structure. For NGC 7538-IRS 11 the magnetic field is aligned with the outflow axis, implying that within the resolution of our observations (14 arcsec FWHM) the circumstellar magnetic field is poloidal. The direction of the molecular outflows, magnetic fields and dust ridges for both IRS 11 and its neighbor IRS1 (60 arcsec/0.9 parsec to the north) are in identical directions. For both DR 21 and NGC 7538-IRS 11 the percentage polarization at the position of the flux peak is low compared to the surrounding points. There is a marked increase in the observed percentage polarization from DR 21 at higher wavelengths. This implies the grain composition cannot be predominantly silicate, but instead is mainly graphite/metallic, and may require grains of different magnetic susceptibility or varying elongation to also be at different temperatures along the observed line of sight.
Minchin Nigel R.
Murray Alexander G.
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