Astrophys. J., 855, 39-39 (2018/March-1)
Polarization properties and magnetic field structures in the high-mass star-forming region W51 observed with ALMA.
KOCH P.M., TANG Y.-W., HO P.T.P., YEN H.-W., SU Y.-N. and TAKAKUWA S.
Abstract (from CDS):
We present the first ALMA dust polarization observations toward the high-mass star-forming regions W51 e2, e8, and W51 North in Band 6 (230 GHz) with a resolution of about 0′′ / . 26 (∼5 mpc). Polarized emission in all three sources is clearly detected and resolved. Measured relative polarization levels are between 0.1% and 10%. While the absolute polarization shows complicated structures, the relative polarization displays the typical anticorrelation with Stokes I, although with a large scatter. Inferred magnetic (B) field morphologies are organized and connected. Detailed substructures are resolved, revealing new features such as comet-shaped B-field morphologies in satellite cores, symmetrically converging B-field zones, and possibly streamlined morphologies. The local B-field dispersion shows some anticorrelation with the relative polarization. Moreover, the lowest polarization percentages together with largest dispersions coincide with B-field convergence zones. We put forward sinω, where ω is the measurable angle between a local B-field orientation and local gravity, as a measure of how effectively the B field can oppose gravity. Maps of sinωfor all three sources show organized structures that suggest a locally varying role of the B field, with some regions where gravity can largely act unaffectedly, possibly in a network of narrow magnetic channels, and other regions where the B field can work maximally against gravity.
© 2018. The American Astronomical Society. All rights reserved.
ISM: individual objects: W51 e2, W51 e8, W51 North - ISM: magnetic fields - polarization - stars: formation
Fig. 1, Table 1: [KTH2018] W51 e8-W (Nos e8-N, e8-S), [KTH2018] W51 NN (Nos N1-N4), [KTH2018] W51N SMA2-E N=1.
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