The JCMT BISTRO Survey: Evidence for Pinched Magnetic Fields in Quiescent Filaments of NGC 1333
The JCMT BISTRO Survey: Evidence for Pinched Magnetic Fields in Quiescent Filaments of NGC 1333
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DOI：
10.3847/2041-8213/ac3cc1
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发表时间：
2021-11
期刊：
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通讯作者：
Y. Doi;K. Tomisaka;T. Hasegawa;Simon Coud'e;D. Arzoumanian;P. Bastien;M. Matsumura;M. Tahani;S. Sadavoy;C. Hull;D. Johnstone;J. Francesco;Y. Shimajiri;R. Furuya;J. Kwon;Motohide Tamura;D. Ward-Thompson;V. J. M. L. Gouellec;Thiem C. Hoang;F. Kirchschlager;J. Hwang;C. Eswaraiah;P. Koch;A. Whitworth;K. Pattle;W. Kwon;Ji-hyun Kang;T. Bourke;Xindi Tang;L. Fanciullo;C. Lee;Hongli Liu;A. Lyo;K. Qiu;S. Lai
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文献类型：
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作者：
Y. Doi;K. Tomisaka;T. Hasegawa;Simon Coud'e;D. Arzoumanian;P. Bastien;M. Matsumura;M. Tahani;S. Sadavoy;C. Hull;D. Johnstone;J. Francesco;Y. Shimajiri;R. Furuya;J. Kwon;Motohide Tamura;D. Ward-Thompson;V. J. M. L. Gouellec;Thiem C. Hoang;F. Kirchschlager;J. Hwang;C. Eswaraiah;P. Koch;A. Whitworth;K. Pattle;W. Kwon;Ji-hyun Kang;T. Bourke;Xindi Tang;L. Fanciullo;C. Lee;Hongli Liu;A. Lyo;K. Qiu;S. Lai
我们使用来自詹姆斯·克拉克·麦克斯韦望远镜恒星形成区域观测调查中 B 场的 850 μm 偏振数据，研究了 NGC 1333 内致密星际细丝的内部 3D 磁结构。理论模型预测，由于细丝的自重力，细丝中的磁场线往往会被径向向内（即收缩）拖向中心轴。我们研究了不受局部恒星形成影响的四段细丝中尘埃发射的总强度（I）和偏振强度（PI）的横截面轮廓，预计这些细丝将保留原始磁场结构。我们发现PI中细丝的半高宽与I中的不同，PI中的两段明显更窄（FWHM比率≃0.7–0.8），而一个片段更宽（FWHM比率≃1.3）。偏振分数 (P) 的细丝轮廓在细丝的脊柱处并未显示最小值，这与通常在分子云和原恒星核心中看到的 P 和 I 之间的反相关性不相符。尘粒排列随密度的变化无法再现观察到的 P 分布。我们通过数值证明，磁流体静力平衡状态下长丝的 I 和 PI 横截面轮廓将根据视角具有不同的相对宽度。因此，在 NGC 1333 中观察到的 FWHM 比率变化与细丝内部收缩磁场结构的模型一致，特别是当它们在磁性上接近临界或超临界时。
We investigate the internal 3D magnetic structure of dense interstellar filaments within NGC 1333 using polarization data at 850 μm from the B-fields In STar-forming Region Observations survey at the James Clerk Maxwell Telescope. Theoretical models predict that the magnetic field lines in a filament will tend to be dragged radially inward (i.e., pinched) toward the central axis due to the filament’s self-gravity. We study the cross-sectional profiles of the total intensity (I) and polarized intensity (PI) of dust emission in four segments of filaments unaffected by local star formation that are expected to retain a pristine magnetic field structure. We find that the filaments’ FWHMs in PI are not the same as those in I, with two segments being appreciably narrower in PI (FWHM ratio ≃0.7–0.8) and one segment being wider (FWHM ratio ≃1.3). The filament profiles of the polarization fraction (P) do not show a minimum at the spine of the filament, which is not in line with an anticorrelation between P and I normally seen in molecular clouds and protostellar cores. Dust grain alignment variation with density cannot reproduce the observed P distribution. We demonstrate numerically that the I and PI cross-sectional profiles of filaments in magnetohydrostatic equilibrium will have differing relative widths depending on the viewing angle. The observed variations of FWHM ratios in NGC 1333 are therefore consistent with models of pinched magnetic field structures inside filaments, especially if they are magnetically near-critical or supercritical.