Polarization Studies with the Submillimeter Array

Magnetic Fields in High Mass Star Formation

High Mass Stars a) G31.41+031: G31.41+0.31 is a high mass star-forming region located 7900 pc away and harbors a massive (500-1500 solar masses) rotating hot molecular core and shows dynamical signatures of collapse. The SMA maps of polarized dust emission (figure 3) clearly show that the magnetic field lines threading the hot core are pinched along the major axis of the core, where the velocity gradient due to rotation is observed, acquiring a hourglass morphology. Mapping of the emission from different spectral lines such as C₃₄S and methanol indicate that angular momentum may not be conserved during the collapse phase and that there is evidence for magnetic braking. These results have also been reported in Science (Girart et al. 2009).


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Figure 3: Polarization in G31.41 (A) Contour map of the 879 µm dust emission superposed on the color image of the polarized flux intensity. Black thick bars indicate the position angle of the magnetic field. The full width half maximum synthesized beam is 1.43" x 0.83" arcsec squared with a position angle of 67 degrees (shown in the bottom left corner). (B) Contours of the 879 µm dust emission superposed on the color image of the flux weighted velocity map of one of the CH₃OH 147-156 A. Black thick bars indicate the direction of the magnetic field (C) Spectrum of the C₃₄S 7-6 line at the position of the dust emission peak (Girart et al. 2009).

High Mass Stars b) G5.89: In this region, which is more evolved than the source G31.41, the magnetic field structures have a complex morphology (Tang et al. 2009). The field structure in G5.89, as seen from the SMA observations, is clearly disturbed by the expansion of the HII region and the molecular outflows in G5.89. From the analysis of the kinematics by using the C₁₇O line emission and the comparison of the energy density (pressure) from the radiation, the magnetic field, and kinetic motions, it is proposed that the field structures are already overwhelmed and dominated by the newly formed massive stars.

References:

D. K. Aitken, J. Greaves, A. Chrysostomou, T. Jenness, W. Holland, J.~H. Hough, D. Pierce-Price, D., J. Richer, Detection of Polarized Millimeter and Submillimeter Emission from Sagittarius A*, 2000, ApJ, 534, L173

A.E. Broderick, A. Loeb, Testing General Relativity with High-Resolution Imaging of Sgr A*, 2006, JPhCS, 54, 448

J. M. Girart, R. Rao, D.P. Marrone, Magnetic Fields in the Formation of Sun-Like Stars, 2006, Science, 313, 812

J. M. Girart, M. T. Beltran, Q. Zhang, R. Rao, R. Estalella, Magnetic Fields in the Formation of Massive Stars, Science, 2009, 324, 1408

R. H. Hildebrand, Magnetic Fields and Stardust, 1988, QJRAS, 29, 327

M.-M. Mac Low, R. S. Klessen, Control of Star Formation by Supersonic Turbulence, 2004, RvMP, 76, 125

D. P. Marrone, J. M. Moran, J. -H. Zhao,R. Rao, The Submillimeter Polarization of Sgr A*, 2006, JPhCS, 54, 354

D. P. Marrone, J. M. Moran, J.-H. Zhao, R. Rao, Interferometric Measurements of Variable 340 GHz Linear Polarization in Sagittarius A* , 2006, ApJ, 640, 308

D.P. Marrone, "Submillimeter Properties of Sagittarius A*: The Polarization and Spectrum from 230 to 690 GHz and the Submillimeter Array Polarimeter,"Ph.D. dissertation, Harvard University, 2006

D. P. Marrone, J. M. Moran, J.-H. Zhao, R. Rao, An Unambiguous Detection of Faraday Rotation in Sagittarius A*, 2007, ApJ, 654, L57

R. Rao, J. M. Girart, D. P. Marrone, S.-P. Lai, S. Schnee, IRAS 16293: A "Magnetic" Tale of Two Cores, 2009, ApJ, 707, 921

Shu, F. H., Galli, D., Lizano, S., Cai, M. J. 2007, IAUS, 243, 249

Y.-W. Tang, P. T. P. Ho, J. M. Girart, R. Rao, P. Koch, S.-P. Lai, Evolution of Magnetic Fields in High Mass Star Formation: SMA dust polarization image of the UCHII region G5.89-0.39, 2009, ApJ, 695, 1399

Y.-W. Tang, P. T. P. Ho, P. M. Koch, J. M. Girart, S.-P. Lai, R. Rao, Evolution of Magnetic Fields in High Mass Star Formation: Linking field geometry and collapse for the W51 e2/e8 cores, 2009, ApJ, 700, 251

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